The body found in a water tank atop a Los Angeles hotel has been identified as that of a missing 21-year-old Vancouver woman, local police say.

Los Angeles Police Department Officer Diana Figueroa confirmed to CBC News late Tuesday that Elisa Lam was found in the Cecil Hotel's rooftop water tank around 10 a.m. local time. Police said body markings led to the identification.

A hotel worker found the body while investigating complaints of low water pressure in the hotel.

Footage from a KTLA news helicopter earlier Tuesday showed firefighters and police officials milling around four large rooftop water tanks, two of which had been opened.

The police are treating the roof as a crime scene, and previously said Lam's disappearance was being considered suspicious, and may involve foul play.

Vancouver resident Elisa Lam was last seen by Cecil Hotel staff Jan. 31. (LAPD/AP)

Los Angeles Fire Dept. Capt. Jamie Moore had previously said the body had posed "no biohazard concerns," though one hotel guest told reporters gathered outside they were disgusted by the idea they were possibly drinking water from that tank.

The LAPD told CBC News that the rooftop had previously been searched, though it's unclear if the water tanks had been checked. There is no security camera on the roof.

LAPD Sgt. Rudy Lopez said anyone could have opened the tanks, but access to "the roof is secured with an alarm, and a lock, and a key to the door access."

Lam was seen acting strangely in the Cecil Hotel elevator. "That [has] worried us, and worried the family," said Lopez.

She was last seen by hotel staff on Jan. 31. It's not clear why she was staying at the Cecil Hotel. Before her disappearance Lam had been in contact daily with her family.

The Cecil Hotel, centre, where the body was discovered, is located in a rough area of Los Angeles. (Google)

The Cecil Hotel is a two-star, 600-room highrise on South Main and 7th streets, a rough area of L.A. It also houses the Stay On Main hotel, which caters to young travellers.

The LAPD told CBC News that its investigation revealed Lam had struggled with depression.

Lam's friends had previously said they were shocked by the disappearance of University of British Columbia student who was hoping to graduate in 2016, and that it was out of character for the young woman not to contact friends or family.

Lam travelled to southern California alone on Jan. 27 for a sightseeing trip, and was said to be on her way to Santa Cruz.

The LAPD said they had been in contact with Lam's family.

With files from The Associated Press