A Chinese-Canadian tourist whose body was found in a water tank on top of a Los Angeles hotel died from accidental drowning, a coroner's official said on Thursday.

Elisa Lam, 21, suffered from bipolar disorder, which was a "significant" factor in her death, investigator Fred Corral of the LA County Coroner's Office said.

Her body was found in the tank on top of the Cecil Hotel in February, three weeks after she went missing.

The cause of death was ruled as "accidental ... due to drowning. Other significant conditions being bipolar disorder."

Asked how Lam got into one of the water tanks, gray cylindrical structures at least 10 feet tall with covered tops, he added: "It appears she climbed in."

Lam, from Vancouver and traveling alone, had been missing since late January, when she stopped making daily contact with her parents.

Security footage from an elevator camera showed her acting strangely.

The case and the video led to widespread speculation about the cause of death, particularly in Canadian and Chinese media.

At one point, she hid in a corner of the elevator, then peered round the corner as if worried someone might be there, seemed to press buttons for multiple floors, and got out and waved her arms around.

Her corpse was eventually found after hotel guests complained of low water pressure in bathroom taps. Experts later concluded that there had been no health dangers to guests.

Management at the Cecil Hotel, in the skid row area of downtown Los Angeles, said rooftop access doors were locked and had alarms, but the four water storage tanks were not locked.

The Coroner's Office investigator declined to give more details of how Lam died, but said doctors had determined that it was an "accidental death".