( CNN ) -- A 21-year-old woman whose body was found in a water tank of a Los Angeles hotel in February was the victim of an accidental drowning , medical examiners reported Thursday . The decomposing body of Elisa Lam floated inside a water tank on the roof of the Cecil Hotel while guests brushed their teeth , bathed and drank water from it for as long as 19 days . A maintenance worker , checking on complaints about the hotel 's water , found the Canadian tourist inside one of four water cisterns . Tests conducted by the city Health Department found no harmful bacteria in the tank or the pipes , which had to be drained , flushed and sanitized after the discovery . Los Angeles robbery-homicide detectives had treated the case as a suspicious death , since falling into a covered water tank behind a locked door on top of a roof would be an unusual accident , Los Angeles Police Sgt . Rudy Lopez said in February . See also : Carbon monoxide is the 'mystery ' cause of 3 North Carolina hotel deaths . Lam checked into the Cecil Hotel on January 26 , on her way to Santa Cruz , California , according to police in her hometown of Vancouver , British Columbia . Five days later , she was seen on a security camera video walking into the elevator , pushing the buttons for four floors and then peering out of the opened elevator door as if she is hiding or looking for someone . Clad in a red hoodie , Lam at one point walks out of the elevator before returning to it , pushing the buttons again . She then stands outside the open elevator doorway , motioning with her hands , before apparently walking away . It was the last day Lam was seen . Lam 's parents reported the University of British Columbia student missing in early February . Her daily calls home stopped on January 31 , police told reporters on February 6 at a Los Angeles news conference . Strange things began happening with the hotel 's water supply later in the month , according to Sabina and Michael Baugh , a British couple who spent eight days there . The water pressure dropped to a trickle at times . `` The shower was awful , '' Sabina Baugh said . `` When you turned the tap on , the water was coming black first for two seconds and then it was going back to normal . '' The tap water `` tasted horrible , '' Baugh said . `` It had a very funny , sweety , disgusting taste . It 's a very strange taste . I can barely describe it . '' But for a week , they never complained . `` We never thought anything of it , '' she said . `` We thought it was just the way it was here . '' Two former guests , Steven and Gloria Cott , filed a class-action lawsuit against the hotel in late February . The lawsuit claims the hotel effectively failed to meet its obligation to provide proper water . `` Instead , the defendants provided water that had been contaminated by human remains and was not fit for human ingestion or to use to wash , '' the lawsuit states , claiming the Cotts believe that water was `` tainted . '' Safety tips for travelers . CNN 's Erica Henry , Alan Duke and Kyung Lah contributed to this report .
Elisa Lam was last seen January 31 . Her parents called to report her missing February 6 . The search for the girl has been expanded from a small area of San Francisco Bay into neighboring counties and includes helicopters, boats and planes. Guests said black water could come out of tap for a few seconds , then run clear .