Las Vegas gunman's girlfriend added to travel watch list: Officials

— -- The companion of the Las Vegas shooter, Stephen Paddock, has been put on a U.S. government watch list as the FBI continues to press her for information about the worst mass shooting in modern American history, federal law enforcement officials told ABC News.

Marilou Danley has been designated a Transportation Security Administration selectee, meaning authorities will be notified if she attempts to board any commercial flight.

The travel designation will require her to undergo extra screening and will notify authorities if she tries to leave the country on a commercial flight, two law enforcement sources told ABC News.

At this stage of the investigation, officials believe that Danley played no part in — and had no knowledge of — her now deceased boyfriend's plan to open fire on concertgoers from the Mandalay Bay hotel last week, killing 58 people and injuring more than 500 others before killing himself.

On Friday, Matthew Lombard, her attorney, told reporters that she continues to cooperate with authorities.

Looking back at the Las Vegas mass shooting

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At least 58 people were killed and hundreds more were injured when a gunman opened fire on a music festival crowd from the 32nd floor of the Mandalay Bay Resort and Casino, Las Vegas, Oct. 1, 2017. The attack is the deadliest mass shooting in modern U.S. history.Pictured: People scramble for shelter at the Route 91 Harvest country music festival, Oct. 1, 2017, in Las Vegas.

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Investigators believe that Danley's relationship with Paddock changed over time, evolving from intimate companion, authorities said, to more of a caretaker for him.

"I knew Stephen Paddock as a kind, caring, quiet man," Danley said in a statement read by her attorney last week. "I loved him and hoped for a quiet future together with him."

She added that she feared, when Paddock bought her a plane ticket to the Philippines and wired her a significant sum of money, that it "was a way of breaking up" with her.

The travel designation, secondary security screening selectee, will appear on her boarding pass at the airport and indicates authorities want to be alerted if Danley, a Philippine native who travels under an Australian passport, makes any effort to travel out of the region or out of the country on a commercial flight.

The designation also gives TSA officers the authority to more aggressively search her luggage.

Officials with the Department of Homeland Security did not respond Monday to questions about Danley's travel status.