Update at 6:37 p.m. ET: Investigators are saying two Iowa cousins who disappeared a week ago have been abducted after a search of the lake where their bikes were found came up empty.

Cousins Lyric Cook-Morrissey, 10, and 8-year-old Elizabeth Collins, went missing July 13 while the pair were riding bikes near Meyers Lake in Evansdale.

Investigators began draining the lake Monday, but stopped at the FBI's request so divers could conduct a search with special sonar equipment, The Associated Press reported. 

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The sonar doesn't work in less than six feet of water.

Black Hawk County Sheriff Chief Deputy Rick Abben told reporters at a news conference Friday that evidence was collected and sent to a lab to be tested. He did not say what the evidence was.

The announcement comes the same day a judge put Lyric’s father, 36-year-old Daniel Morrissey, on pretrial supervision until September when he is scheduled to face drug charges.

Authorities said Morrissey and his wife, Misty Cook-Morrissey, 34, stopped cooperating with police as of Thursday, The AP reported.

The AP reported Abben said neither is considered a suspect and wasn't sure why they had stopped talking with police. 

Related: Families of missing Iowa girls fear they were kidnapped

Cook's sister, Tammy Brousseau, told the AP the girl's parents felt like they were being treated as suspects. Both stopped cooperating after their attorney advised them to do so. 

"They've been cooperating with the police 100 percent, but because police don't have a silver Cadillac that tore off with the kids, they don't have no leads," she told AP. 

Cook told the Des Moines Register Thursday that Daniel walked out of a police interview earlier in the week after police accused him of killing the two girls. 

Authorities also have sifted through trash, examined a laptop and computer, and dug into the parents' past criminal histories. 

Cook has a meth-related drug charge from 10 years ago and Daniel has multiple drug charges along with burglary and domestic assault. 

Morrissey is charged with possession of methamphetamine with intent to deliver conspiracy to manufacture methamphetamine and other crimes.

The Register reported Morrissey's eight-year marriage to Cook has been rocky at times. The domestic assault charges stems from a 2011 incident where Cook told police he smashed her face into the floor and placed his knee over her neck, making it difficult for her to breathe.

Brousseau told the station the pair had a no contact order with each other but has since been modified since both girls went missing. 

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James R. Evans / U.S. Pacific Fleet

Dolphins surface as the USS Halsey destroyer maneuvers off Southern California on Sept. 30, 2011.

New Navy estimates showing many more dolphins, whales and other marine mammals could be hurt by sonar off Hawaii and Southern California caused alarm among environmentalists on Friday. The Navy, for its part, emphasized those were worst-case estimates and that the numbers cover a much larger testing area than before.

The numbers are in the Navy's new draft environmental impact statement for exercises planned from 2014-2018. In it, the Navy says that, under its preferred alternative, sonar training and testing might unintentionally harm marine mammals 2.8 million times a year over five years.

"The numbers are staggering and there is absolutely no corresponding mitigation to account for this harm," Zak Smith, an attorney for the Natural Resources Defense Council, told msnbc.com.

That's up from about 150,000 instances a year in the Navy's impact statement for 2009-2013, Smith added.

But the Navy said the numbers were misleading since the new area is much larger and more activities have been added since the last statement. "It's like comparing three grapes to a watermelon," Pacific Fleet spokesman Mark Matsunaga told msnbc.com.

"These are just worst-case estimates," he added. "That's not to say we're going to go out there and hurt them all."

"Direct comparisons with the prior analysis might not be comparing apples to apples," acknowleged Smith. "But I think that's irrelevant. ... Regardless of what accounts for this change the fact is that we -- including the Navy -- now understand that the Navy's activities will have a much greater impact than previously thought."

Twelve million potential exposures over those five years are listed under "behavioral," Smith noted. It's the least harmful category, but Smith said it can include an impact like forcing a whale to abandon its habitat for several days. "Marine mammals don't have the energy to continually withstand" that kind of impact, he added.

Two million incidents are counted for temporary hearing loss, Smith said, and 2,000 are listed for permanent hearing loss.

Hearing is critical to marine mammals, much like seeing is to humans, Smith said. "It's as if some technology used in my neighborhood blinded me for the next 10 minutes. It becomes a problem if I go outside and get hit by a car."

Dolphins are the most impacted species under the new estimates, which are based on models, followed by whales and orcas.

In addition, the Navy estimates traditional explosives testing and training might kill 1,000 marine mammals during the period.

The Navy numbers were presented Thursday by John Van Name, a senior environmental planner at the U.S. Pacific Fleet.

US sued over sonar tests in whale waters

"Each time around, each time we swing through this process, we get better, we take a harder look, we become more inclusive," the Associated Press quoted him as saying.

Matsunaga added that the new estimates include "more activities that weren't analyzed the first time around" and "hundreds more sources of sound" from Navy ships.

"We're at an early stage of the process," said Matsunaga, noting that the estimates don't take into account Navy mitigation.

Smith said his group isn't looking to block sonar and explosives testing and training, but to see it used at times and places where the impacts to marine mammals are minimized.

Will the Navy work with other federal agencies to mitigate the damage?

"That's the big question," said Smith, noting that, as part of the environmental process, the Navy is now taking public comments and then will consult with the National Marine Fisheries Service. 

The NRDC, he added, will be submitting formal comments and hopes that the Navy and the fisheries service will eventually have "a very thoughtful conversation as to what they can work out."

Public comment on the draft environmental impact statement is being accepted at http://hstteis.com.   

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