Elisa Lam, 21, was found dead in a water tank on the roof of the Cecil Hotel in February 2013

New details of Elisa Lam's mysterious death at The Cecil Hotel in 2013 have emerged, including how a police dog found a trace of her scent at a window leading onto a fire escape after her naked body was found floating in a water tank on the roof.

Lam's death remains unsolved to this day.

On February 19 2013, the 21-year-old Canadian student was found floating naked in a water tank on the roof of The Cecil Hotel in Los Angeles after guests complained that the water in their rooms was dark and smelly.

Police believe Lam, who was bipolar and had been staying at the hotel, had been there for two weeks by the time she was found.

She checked into the hotel on January 26 after traveling from British Columbia, Canada, where she was studying, on her way to Santa Cruz. On January 31, Lam stopped using her phone. She was last seen in surveillance footage on February 1 behaving strangely in the hotel elevator, appearing to hide from someone or something.

No other information about her final movements - including how she got onto the roof and into the water tank - has been confirmed.

But in a new episode of HLN'S Real Life Nightmare, a former LAPD detective revealed that a police reveals that a sniffer dog picked up her scent at a window which led onto a fire escape in the building.

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Lam's naked body was found in one of these four water tanks. How she got there remains a mystery to this day

Fire crews are pictured leaving the hotel in February 2013 after discovering her body

In a clip shared exclusively with DailyMail.com, retired LAPD homicide detective Greg Kading says: 'Most people don't know that there was an alert.

'The dog did go down a hallway and alert at a window and that window leads directly out to the fire escape.'

Once outside, however, the dog lost the scent.

'There was at least an initial indication that she had gone down the hallway and went out this window, onto the fire escape,' he added.

Lam's death was officially ruled accidental but how she died and the details leading up to it remain a mystery.

There were no obvious traces of alcohol or illegal drugs in her system when she died. Her family said she had been taking medication to treat her bipolar disorder.

On January 31, she stopped using her phone.

Retired LAPD homicide detective Greg Kading said in a new episode of Real Life Nightmare that sniffer dogs picked up Lam's scent on a window leading on to a fire escape

The video on February 1 - which went viral after police shared it and sparked theories that the hotel was haunted - was the last time she was seen alive.

It is troubling footage which shows her entering the elevator, staring at the buttons.

At first, she appears calm.

Suddenly, she is filmed leering forward and looking side to side into the hallway.

Lam then jumped back into the elevator, then out again.

She entered the elevator again and frantically started pressing the buttons then got out and was filmed waving her hands through the air bizarrely then running off.

Cheryl Arutt, a forensic psychologist, said in the new episode of Real Life Nightmare: 'At one point it looked like maybe she was hiding from someone.

'She seemed to be hiding in a corner, trying to make herself small land be out of sight.

'That was one of the moments that was rather odd.'

The hotel is now called the Main Hotel and was, at the time, a well-known if somewhat seedy institution favored by low-income and elderly people.

It is unclear who Lam had come into contact with, if anyone, when she was staying there.

Her family reported her missing at the start of February, several days before she was found.

The story erupted after guests at the hotel started complaining that the water in their rooms was either dirty, had a smell or not working properly.

This is the last time Lam was seen alive. She is shown in surveillance taken inside an elevator in the hotel where she behaved strangely, as if she was hiding from someone in the hallway

One British couple who were interviewed said it would come out from the faucet black whenever they turned it on.

A maintenance man was sent to check on the water towers, and that is when Lam's body was found.

Lam's death was ruled an accidental drowning

Whether or not she was the victim of foul play remains undetermined.

Experts have called into question how likely it is that she will have been able to not only get up to the roof but to undress herself and lift the lid on the water tank before climbing inside.

There is however no proof that anyone besides her was on the roof when she died, and exactly how long she had been in the water beforehand is also unclear.

In the new episode of Real Life Nightmare,

'We're talking about a young lady who is not by any standards large, we're talking bout 120lbs, that can climb that ladder, single-handedly push that lid off, which weighs only about 20 or so lbs but which takes some effort, you have to think maybe something else was involved? Another person?' said one commentator.

'The fact that she would have had to have taken all of these steps, really makes you wonder - was there foul play?' another asked.

Journalists who were among the first to the scene were also interviewed.

Kyung Lah, a CNN reporter, recalled: 'The first people I saw were a British couple. They had been at the hotel eight days and they then told a revolting story.

'I don't know how else to put it.'

The woman in the couple said: 'There was something wrong... the water when you turn it it was black for two seconds then it was going back to normal.'

Tourists had been using it as drinking water, were bathing in it and were brushing their teeth with it.

The hotel became the inspiration for a series of American Horror Story.

Lam's mysterious death will be revisited in Deadly Hotel Check-In, an episode of Real Life Nightmare, which premieres Saturday, November 30, 2019, 8pm-9pm ET.