Analysis of the video released soon after Elisa Lam disappeared from the Cecil hotel in Los Angeles suggests the Canadian tourist may have been under the influence of ecstasy when she vanished.
Lam's body was found floating in the hotel's water tank on 19 February, and it is thought the corpse could have been there for up to 19 days.
The 21-year-old was last seen behaving strangely in a hotel elevator, frantically walking in and out of the car and peeping out nervously into the corridor, while making hand gestures and talking to nobody.
CCTV footage of Lam in the elevator, released by the Los Angeles Police Department, has now been analysed by club-drug expert Trinka Porrata.
When asked about the possibility of drug use, Porrata told LA Weekly that it is "hard to say." However she said Lam's behavior does show signs of the influence of Ecstasy.
"She's "petting" something and then dancing a bit. Could be an Ecstasy pill that contains MDMA plus some other hallucinogen," Porrata said.
"Getting into the corner of the elevator and looking out repeatedly could seem like paranoia or just part of her hallucination. Hard to say from just that little bit. Even harder of course to guess whether it was something she took voluntarily or was slipped to her.
"Ecstasy IS considered a rape drug but so many pills called Ecstasy [are often] a mixture or something else completely that they don't get the desired effects for a sexual assault," Porrata added.
The analyst also said that people under the influence of MDMA can have hallucinations and there is a possibility of them wandering away to strange places. However, she asserted that Lam's decision to head up to the hotel water tank is not the typical behaviour of a person on Ecstasy.
According to Porrata, the water tank was "a weird place to end up," unless Lam reached the tank involuntarily. However "people under the influence of [the hallucinogen] PCP may like going near water. It does have a "tendency to 'attract' people to water."
After an initial autopsy proved inconclusive, a toxicology result is likely to confirm whetherLam was actually under the influence of any drug. This may take another four to six weeks.
See a video of the elevator footage here:
(Video courtsey: YouTube/MrFrankPreciado)
Meanwhile, a BBC report suggests that American actor Robert Conrad gave a couple from Plymouth $500 (£330) after they had to leave Cecil hotel when Lam's body was discovered in the water tank.
Twenty-seven-year-old Sabina Baugh, along with her husband Michael, had spent several nights at the Cecil Hotel when Lam's body was found.
The couple not only took a shower and brushed their teeth with the water, but also drank from the tap.
"The water did have a very funny, disgusting taste. We never thought anything of it. We thought it was just the way it was here," Sabina Baugh told Mail Online in an earlier report.
"The moment we found out, we felt sick to the stomach, quite literally. We're not well mentally. It's the psychological stuff. If you think about it, it's not good," her husband Michael Baugh had said.
The couple immediately relocated to another part of the city as authorities tested the water, although they subsequently concluded it posed no health threats.
Sabina Baugh told BBC that Conrad, best known for the 1960s television series The Wild Wild West, gave them the money after he heard about their story on the radio.