Stephen Paddock's Girlfriend Marilou Danley Under Travel Surveillance

Stephen Paddock's long-time girlfriend, Marilou Danley, was added to U.S. government's travel watch list on Wednesday as investigations continue to find the motive behind the Las Vegas shooting.

Danley's travels will be under heavier scrutiny and subject to secondary searches by airport officials, as she was labeled as U.S. Transportation Security Administration "selectee." Traveling on an Australian passport, Danley's possible international travels will also be directly reported to authorities, according to two law enforcement officials cited in an ABC News report.

Danley is not seen as a suspect at this point in the investigation since she was in the Philippines during the planning and execution of Paddock’s actions. However, she is still a prime witness to the life of Paddock. Danley's lawyer, Matthew Lombard, made a statement on her behalf October 4.

"I knew Stephen Paddock as a kind, caring, quiet man," Danley said in a statement last week. "He never said anything to me, or took any action that I was aware of that I understood in any way to be a warning that something horrible like this was going to happen."

Paddock bought over 30 guns within the span of 12 months, and orchestrated the deadliest mass shooting in modern U.S. history. From the 32nd floor of the Mandalay Bay Hotel, Paddock fired continuous bullets on the 22,000 attendees of the Route 91 Harvest Festival. He killed at least 58 people and injured more than 500.

Lombard told reporters on Friday that Danley continues to cooperate with officials. It's possible Paddock and Danley's relationship transformed over time into more of a caregiver companionship, with Danley apparently taking care of Paddock.

"We are still speaking with Ms. Danley about the suspect’s movements, gun purchases and anything else we need to know about him and how he had planned his assault, and who he came into contact with during the planning phase," said Las Vegas Metropolitan Police Department Sheriff Joseph Lombardo at a press conference on Monday. "Every piece of information we get is one more piece of the puzzle."