Lm Otero / AP

Investigators said ammonium nitrate caused the explosion at a fertilizer plant in West, Texas, on April 17. Fourteen people died and more than 200 more were injured in the blast.

Investigators have determined that ammonium nitrate was the cause of the explosion at a West, Texas, fertilizer plant last month that killed 14 people and injured some 200 more, a spokeswoman for the Texas state fire marshal's office said Tuesday.

"The investigators have been able to narrow down the origin to the fertilizer and seed building on site, and we also know that what caused the explosion was the ammonium nitrate," said Rachel Moreno, a spokeswoman for the Texas State Fire Marshal's Office. "What we don't know is exactly why."

The fire marshal's office has been leading the investigation of the April 17 blast, along with the federal Alcohol, Tobacco, Firearms and Explosives agency (ATF).

Ammonium nitrate is a dry fertilizer mixed with other fertilizers such as phosphate and applied to crops to promote growth. It can be combustible under certain conditions, and was used as an ingredient in the Oklahoma City bombing in 1995 that left 168 people dead.

Slideshow: Fertilizer plant explosion in Texas

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A huge blast rocked a small Texas town, killing 14 people and injuring some 200 more.

Launch slideshow

Handout / Reuters

Seattle police officers perform a skit that mocks the homeless in this still image from a portion of a 1986 training video released by the Seattle Police Department.

SEATTLE -- Seattle's interim police chief has apologized for appearing in a 1986 video that showed him and other officers mocking the homeless in what the city's police department this week called an "ugly piece" of its history.

Interim Chief Jim Pugel, who is implementing sweeping reforms in the wake of a 2012 U.S. Department of Justice report that found the city's police routinely used excessive force, appeared in the video when he was a 26-year-old officer.

In the roughly five-minute clip, which officials say was part of a training video and which they released this week, Pugel and a few colleagues are seen wearing fake beards, dancing with bottles of alcohol under a freeway overpass and singing parody lyrics to the 1964 song "Under the Boardwalk" by The Drifters.

Some of the officers sport blacked-out teeth as they croon lyrics such as, "We'll be drinking Thunderbird (wine) all through the day, under the viaduct. Who could ask for anything more?"

"Even by 1980s standards, the Seattle Police Department considered the video to be insensitive and inappropriate," Pugel, who was appointed to his position earlier this month, said in a statement late on Thursday. "I regret my participation and have professionally apologized for my role in it. I do so now publicly. I am truly sorry."

He takes over a department that has at times experienced a troubled history with minority communities and is in the first year of a reform plan overseen by the U.S. Department of Justice to revise the use of force by officers.

The Seattle Times reported in a story posted on its website on Friday that the newspaper and other media outlets had received several tips about the video's existence before it was made public late on Thursday by police.

Seattle police spokesman Sean Whitcomb said Pugel, who has not said whether he will seek to lead the department on a permanent basis, disclosed the existence of the video to other city officials and homeless groups when he was appointed interim chief.

"It's not a problem but an opportunity to showcase who Chief Pugel is," Whitcomb said. "For him it was a leadership moment."

Police say all existing copies of the video have been destroyed, except for a single copy retained for their records.

Pugel said in his statement that he had the video released because he felt it was "important to show where this department has been and where it is going" and that he discussed it with Mayor Mike McGinn and several Seattle-based homeless groups.

David Goldman/AP

Atlanta Public Schools defendant Sandra Ward, right, turns herself in at the Fulton County Jail accompanied by her attorney Robbin Shipp on April 2 in Atlanta.

Former educators indicted in a cheating scandal that has rocked Atlanta's public school system began turning themselves in to authorities on Tuesday, ahead of a deadline to surrender voluntarily.

At least three of the 35 former Atlanta public school educators indicted by a grand jury last week had reported to the Fulton County jail by mid-morning, according to jail records.

They face charges including racketeering and making false statements for allegedly conspiring to alter and improve standardized test scores to obtain cash bonuses, according to prosecutors.

Former Atlanta School Superintendent Beverly Hall was among the former teachers, principals and administrators named in the 65-count indictment returned on Friday. She was not among the first defendants who turned themselves in.

All of the defendants have been given a Tuesday deadline by the Fulton County district attorney's office to surrender or face arrest in their homes or workplaces.

Hall was named National Superintendent of the Year by the American Association of School Administrators in 2009, the same year prosecutors contend widespread cheating took place.

She received a $78,000 bonus that year from the school system for improving its test scores, prosecutors said.

"The money she received, we are alleging, was ill gotten and it was theft," Fulton County District Attorney Paul Howard said at a news conference on Friday.

Related:

School cheating investigation puts Atlanta teachers, principals at center of scandal

WASHINGTON -- More than 200 businesses on Wednesday urged the U.S. Supreme Court to strike down a federal law that restricts the definition of marriage to heterosexual unions, in one of corporate America's most prominent efforts to support same-sex marriage.

The companies signed on to a friend-of-the-court brief in Windsor v. United States, a high-profile case challenging the 1996 federal Defense of Marriage Act (DOMA). They ranged from technology giants Microsoft Corp and Google Inc to Wall Street financiers such as Citigroup Inc and Goldman Sachs Group Inc to vineyards and yogurt makers in California.

Thomson Reuters Corp, which owns the Reuters news agency, also supported the submission.

The companies want the Supreme Court to void a key provision in the federal law that defines marriage as a union between a man and a woman. They largely stayed away from constitutional arguments attacking the law and instead focused on the business nuisance the law created.

DOMA forces employers to treat employees with same-sex spouses differently from those with opposite-sex partners, the companies said, depriving gay employees of certain healthcare and retirement benefits that may be on offer. The law also creates headaches for human resources officials, they said.

"HR departments would tell you it is a disaster trying to deal with DOMA when you are a large employer, because you have these employees who are legally married, but now you've got to put them in a different box for W-2s, for ERISA (Employee Retirement Income Security Act), for retirement benefits, and it's really vexing," said Sabin Willett in an interview. Willett wrote the brief for his law firm, Bingham McCutchen, which handled the matter pro bono.

Separately, lawyers representing another group of employers, including some of the same companies, said they planned to file a brief on Thursday in a related case that questions a California law, known as Proposition 8, banning gay marriage.

The two cases are to be argued before the Supreme Court on March 26 and 27. A decision is expected by the end of June.

While corporate America has long offered domestic partnership benefits and made efforts to attract gay employees, the filing seemed to represent a new step in an effort to promote the issue.

"It is old news that big business is friendly to lesbian and gay unions," said Yale law professor William Eskridge, who has argued on behalf of gay rights. "But there has never been a business brief quite like this one with so many signatories on such a landmark issue," he said.

A group of prominent Republicans, including former advisers to President George W. Bush, are also expected to file a brief challenging the California law, adding heft to backers of gay rights.

The arguments appeared directed at Justice Anthony Kennedy, as a moderate and potential swing vote, to show the kind of wide support that exists, Eskridge said.

'HURTING BUSINESS'

The brief grew out of a previous effort to represent business interests in another case challenging the DOMA law, according to Willett.

That case brought together some 70 companies that felt courts may not have understood the full business impact of the law.

"When people talk about DOMA, they usually, and rightly so, focus on its impact upon human beings ... but people may not realize, and courts may not realize, this thing is hurting business, too," Willett said.

In the brief filed on Wednesday, the companies argued that DOMA "requires that employers treat one employee differently from another, when each is married, and each marriage is equally lawful."

DOMA does not create any uniformity nationwide, they said, because 12 states either authorize same-sex marriage or recognize marriages that have been performed in other states.

That creates a burden for employers, particularly those who do business nationally, they added.

The law also forces companies to discriminate, sometimes in contravention of their own internal policies and local laws, when dealing with healthcare plans and other benefits, the companies said.

In briefs already filed in support of restricting marriage to heterosexual unions, business interests have not been represented. The U.S. Chamber of Commerce has not taken a stand on the issue.

A leading U.S. nuclear weapons laboratory recently discovered its computer systems contained some Chinese-made network switches and replaced at least two components because of national security concerns, a document shows.

A letter from the Los Alamos National Laboratory in New Mexico, dated November 5, 2012, states that the research facility had installed devices made by H3C Technologies Co, based in Hangzhou, China, according to a copy seen by Reuters. H3C began as a joint venture between China's Huawei Technologies Co and 3Com Corp, a U.S. tech firm, and was once called Huawei-3Com. Hewlett Packard Co acquired the firm in 2010.

The discovery raises questions about procurement practices by U.S. departments responsible for national security. The U.S. government and Congress have raised concerns about Huawei and its alleged ties to the Chinese military and government. The company, the world's second-largest telecommunications equipment maker, denies its products pose any security risk or that the Chinese military influences its business.

Switches are used to manage data traffic on computer networks. The exact number of Chinese-made switches installed at Los Alamos, how or when they were acquired, and whether they were placed in sensitive systems or pose any security risks, remains unclear. The laboratory - where the first atomic bomb was designed - is responsible for maintaining America's arsenal of nuclear weapons.

A spokesman for the Los Alamos lab referred enquiries to the Department of Energy's National Nuclear Security Administration, or NNSA, which declined to comment.

The November 5 letter seen by Reuters was written by the acting chief information officer at the Los Alamos lab and addressed to the NNSA's assistant manager for safeguards and security. It states that in October a network engineer at the lab - who the letter does not identify - alerted officials that H3C devices "were beginning to be installed in" its networks.

The letter says a working group of specialists, some from the lab's counter intelligence unit, began investigating, "focusing on sensitive networks." The lab "determined that a small number of the devices installed in one network were H3C devices. Two devices used in isolated cases were promptly replaced," the letter states.

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The letter suggests other H3C devices may still be installed. It states that the lab was investigating "replacing any remaining H3C network switch devices as quickly as possible," including "older switches" in "both sensitive and unclassified networks as part of the normal life-cycle maintenance effort." The letter adds that the lab was conducting a formal assessment to determine "any potential risk associated with any H3C devices that may remain in service until replacements can be obtained."

"We would like to emphasize that (Los Alamos) has taken this issue seriously, and implemented expeditious and proactive steps to address it," the letter states.

Corporate filings show Huawei sold its stake in H3C to 3Com in 2007. Nevertheless, H3C's website still describes Huawei as one of its "global strategic partners" and states it is working with it "to deliver advanced, cost-efficient and environmental-friendly products."

The Los Alamos letter appears to have been written in response to a request last year by the House Armed Services Committee for the Department of Energy (DoE) to report on any "supply chain risks."

In its request, the committee said it was concerned by a Government Accountability Office report last year that found a number of national security-related departments had not taken appropriate measures to guard against risks posed by their computer-equipment suppliers. The report said federal agencies are not required to track whether any of their telecoms networks contain foreign-developed products.

The Armed Services committee specifically asked the DoE to evaluate whether it, or any of its major contractors, were using technology produced by Huawei or ZTE Corp, another Chinese telecoms equipment maker. ZTE Corp denies its products pose any security risk.

In 2008, Huawei and private equity firm Bain Capital were forced to give up their bid for 3Com after a U.S. panel rejected the deal because of national security concerns. Three years later, Huawei abandoned its acquisition of some assets from U.S. server technology firm 3Leaf, bowing to pressure from the Committee on Foreign Investment in the United States. The committee evaluates whether foreign control of a U.S. business poses national security risks.

In October, the House Intelligence Committee issued an investigative report that recommended U.S. government systems should not include Huawei or ZTE components. The report said that based on classified and unclassified information, Huawei and ZTE "cannot be trusted to be free of foreign state influence" and pose "a security threat to the United States and to our systems."

William Plummer, Huawei's vice president of external affairs in Washington, said in an email to Reuters: "There has never been a shred of substantive proof that Huawei gear is any less secure than that of our competitors, all of which rely on common global standards, supply chains, coding and manufacturing.

"Blackballing legitimate multinationals based on country of origin is reckless, both in terms of fostering a dangerously false sense of cyber-security and in threatening the free and fair global trading system that the U.S. has championed for the last 60-plus years."

He referred questions about H3C products to Hewlett Packard. An HP spokesman said Huawei no longer designs any H3C hardware and that the company "became independent operationally ... from Huawei" several years prior to HP's acquisition of it. He added that HP's networking division "has considerable resources dedicated to compliance with all legal and regulatory requirements involving system security, global trade and customer privacy."

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