The girlfriend of the retiree who killed 58 people in a massacre in Las Vegas is returning to the United States from the Philippines, sources at Manila's international airport said on Wednesday.

Marilou Danley, who U.S. authorities have said is a "person of interest" in the investigation, left on Tuesday evening, police and immigration sources told Reuters. She arrived in Manila in September, they said.

"Her trip back to the U.S. was coordinated with FBI authorities," a police official said. Danley had left Manila unescorted but would be met by FBI on her arrival in the United States, the official said.

He said she was returning to clear her name of any involvement in the worst mass shooting in modern U.S. history.

Stephen Paddock, who killed himself moments before police stormed the hotel suite he had transformed into a sniper's nest on Sunday night, left no clear clues about why he staged his attack on an outdoor concert below the high-rise building.

Law enforcement authorities are hoping to obtain some answers from Danley, who has been identified as Paddock's live-in companion.

The Philippine police official said authorities in Manila were told that Paddock used identification belonging to Danley, who has an Australian passport, when checking in to the Las Vegas hotel.