Police are investigating the death of a 23-year-old woman whose body was found on a sidewalk outside her boyfriend's five-story apartment building.

Linda Thu Thu Nguyen of Garden Grove is believed to have fallen from the roof of the Anavia apartments at 2045 S. State College Blvd., Anaheim police Sgt. Rick Martinez said.

Physical evidence found on the roof showed Nguyen accessed the rooftop, but it was unclear what she was doing there, Martinez said.

Authorities do not think she was pushed. They say she may have been trying to get back into her boyfriend's apartment.

Nguyen spent time with her boyfriend Saturday night and left, Martinez said, adding that her boyfriend was unaware that she was still in the apartment complex.

"He didn't hear anything," Martinez said.

An autopsy performed on Monday showed she died of injuries consistent with a fall, he said.

"There's nothing to indicate foul play, but it's still an open investigation," Martinez said.

Martinez said alcohol is believed to have played a role.