Lam's body was found Tuesday morning at the bottom of one cistern that was about three-quarters full of water, Lopez said.
The opening at the top of the cistern is too small to accommodate firefighters and equipment, so they had to cut a hole in the storage tank to recover Lam's body.
The cisterns are on a platform at least 10 feet above the roof.
To get to the tanks, someone would have to go to the top floor then take a staircase with a locked door and emergency alarm preventing roof access.
Another ladder would have to be taken to the platform and a person would have to climb the side of the tank.
Lopez said there are no security cameras on the roof.
Lam intended to travel to Santa Cruz, about 350 miles north of Los Angeles. Officials said she tended to use public transportation and had been in touch with her family daily until she disappeared.
The Cecil Hotel was built in the 1920s and refurbished several years ago. The hotel is on Main Street in a part of downtown where efforts at gentrification often conflicts with homelessness and crime. It had once been the occasional home of infamous serial killers such as Richard Ramirez, known as the Night Stalker, and Austrian prison author Jack Unterweger, who was convicted of murdering nine prostitutes in Europe and the U.S., the Los Angeles Times reported.
By noon Wednesday, the Cecil Hotel had relocated 27 rooms used by guests to another hotel, but 11 rooms remained filled, Powell said. Those who chose to remain in the hotel were required to sign a waiver in which they acknowledged being informed of the health risks and were being provided bottled water, Powell said.
Baugh and his wife, who were on their first trip to the U.S., had planned to go to SeaWorld on Wednesday. Instead, they were trying to find a new hotel. Their tour agency placed them in another downtown hotel with a less than sterling reputation, from what they heard.
"We're just going from one dodgy place to another," Baugh said, resigned, "but at least there's water."
Tami Abdollah can be reached at http://www.twitter.com/latams. Shaya Tayefe Mohajer contributed to this report.