A Southwest Airlines flight carrying 143 passengers from Los Angeles to Austin, Texas, was diverted and forced to land in Phoenix on Monday evening after a bomb threat was phoned in, officials said.

While the plane was in the air, U.S. F-16 fighter jets were sent to monitor the situation, Michael Kucharek, a spokesman for the joint U.S.-Canadian North American Aerospace Defense Command (NORAD), told Reuters.

Southwest Airlines flight 2675 landed safely in Phoenix Sky Harbor International Airport, where passengers were removed from the plane, an airline spokesperson said.

“Out of an abundance of caution, the captain of Southwest Airlines flight 2675, en route from Los Angeles to Austin, safely landed in Phoenix to look into a possible security threat,” the airline said in a statement.

Phoenix police and FBI bomb technicians searched the plane and found no explosive devices, FBI spokesman Manuel Johnson said. Law enforcement agents also interviewed all of the passengers. A screening of luggage by federal TSA agents was under way late into the evening.

Johnson said an investigation into the caller who initiated the threat was continuing.

The flight was diverted at the request of the Los Angeles Police Department, according to Southwest and the FBI. 

Upon landing in Phoenix, the Boeing 737-700 was isolated at the airport away from the main passenger terminal.

Other flights in and out of Sky Harbor airport were arriving and departing as scheduled.

All evacuated passengers were to be taken to Austin "as soon as possible," Southwest Airlines spokeswoman Katie McDonald said. 

Reuters contributed to this report.

The claim that "everything is bigger in Texas" will likely gain further credence later this year, when the speed limit on a stretch of toll road between Austin and San Antonio hits 85 miles per hour — the highest limit in the country.

Constructions crews on Wednesday began posting 85-mph speed limit signs along a pending section of toll road on Texas' State Highway 130. This 41-mile stretch of highway, which will open for traffic by Nov. 11, is on the east side of Austin and heads southwest toward San Antonio.

Chris Lippincott, an official with the State Highway 130 Concession Co., said that the Texas Department of Transportation has determined that this area is safe to travel at 85 mph.

Related: Texas studies 85-mph speed limit, fastest in US

"We are committed to operating a safe, reliable highway for our customers," Lippincott said in a statement. "On any road, drivers hold the key to safety based on traffic, travel conditions and the capabilities of their own vehicles."

Since the repeal of the 55-mph national speed limit for U.S. highways in 1995, 34 states have individually raised their speed limits to 70 mph or higher on portions of their roads, according to the Governors Highway Safety Association.

Other roads in the Lone Star State also have high speed limits: On some highways in rural West Texas, drivers can legally cruise as fast as 80 mph, The Associated Press reported. Utah is the only other state in the country with posted speeds at 80 mph, with that as the limit on portions of Interstate 15, according to the Insurance Institute for Highway Safety.

The Insurance Institute for Highway Safety believes higher speed limits have a costly trade-off.

"There’s a clear safety downside to raising safety limits," spokesperson Russ Rader told NBC News. "The research is absolutely clear that high speed limits lead to higher crash deaths."

Rader cited a 2009 study that found that in more than 10 years of follow-up after the 1995 federal speed limit repeal, an estimated 12,545 American deaths were attributed to increased speed limits.

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"If safety were a priorty, states would not be raising speed limits," Rader said. "They would be finding ways to heavily enforce speed limits they have."

The National Motorists Association, an advocacy organization originally rooted in fighting the 55-mph national limit, believes higher speeds are a "win-win" situation.

"Based on what we have heard about it, the Texas Department of Transportation did in fact do their required homework to make this happen," spokesperson John Bowman said.

Related: Robot cars could increase highway efficiency 273 percent, study says

"The prevailing wisdom is setting the speed low," Bowman said, so there is a pressure to set low speed limits. However, he said they believe that legitimate studies often find that the speeds on roads should be raised.

"There’s a myth that when you increase speed limits, accidents and fatalities go up," Bowman claimed.

According to Bowman, higher speeds can actually increase highway safety by letting traffic flow at is own rate, reducing conflicts between vehicles, less stopping and starting, and fewer quick lane changes.

The Associated Press contributed to this report.

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AUSTIN, Texas -- Linda Gatica survived head injuries caused by child abuse when she was a baby, but more than three decades later they killed her in what Texas police are now calling a murder.

Yet investigators said on Thursday they aren't hunting for a suspect in the murder of Gatica, who was 36 when she died in May at an Austin care facility for people with mental disabilities.

That's because they believe the killer to be Gatica's long-dead grandmother, Martha Gatica, who abused her when she was four months old.

"Investigators learned that Linda was brought to a hospital by her mother in 1976 with head injuries that appeared suspicious," Austin police said in a statement.

Police weren't notified at the time, but Child Protective Services investigated and baby Linda was removed from her family and placed in foster care, the statement said.

'Out of the norm'
Retracing the CPS' probe, police found that the Linda Gatica's mother, Mary Jane Gatica, who was 20 at the time, had given a caseworkers differing accounts of how her daughter may have been hurt, including that she may have fallen off the bed or slipped on a toy, Austin's statesman.com reported.

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Mary Jane Gatica and her three children lived with her mother at the time, the newspaper reported. 

After her death decades later, authorities concluded that the injuries suffered when she was a baby ultimately killed Linda Gatica. Further details on the injuries were not available. Police detectives decided to clear the case since the person who abused Gatica -- her grandmother -- is no longer alive.

"It's out of the norm," Austin Police Corporal Anthony Hipolito said of the case.

Reuters and NBC News staff contributed to this report. 

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A police officer was fatally shot early Friday at a Wal-Mart store in Austin, Texas, and a suspect is in custody.

Senior Police Officer Jaime Padron was shot in the neck and died at the scene, Austin Police Chief Art Acevedo said, adding that Padron left behind two daughters, ages 10 and six.

Acevedo said the officer was responding to a routine call about a drunk man in the store.

KUT News reported that when the officer arrived at the scene, the suspect began to fight him. The suspect then pulled out a semi-automatic pistol, according to police, and shot the officer in the neck.

The officer was able to radio for help, KUT said, but he later died in the store.

Acevedo said two Wal-Mart employees tackled the suspect after the shooting and held him until another police officer arrived and arrested him.

Brandon Montgomery Daniel, 24, was booked into the Travis County jail on capital murder charges in connection with the shooting, according to jail records. If convicted of capital murder, Daniel could face the death penalty.

Acevedo said he would like to see the shooter face murder charges.

"It is a tragedy on Good Friday to lose an officer like this, but it is part of what these men and women do," Acevedo said, according to KWTX.com. "They know when they become a police officer that this is a sacrifice they are willing to make."

The Associated Press contributed to this report.

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