KNBC-TV, Los Angeles, reported Elisa Lam, 21, hadn't been seen for weeks after checking into the Cecil Hotel Jan. 26.
Her parents said she called them every day of her visit to California until the last day she was seen by another person Jan. 31. Officials said Lam can be seen in hotel surveillance video Feb. 1 inside an elevator acting erratically.
Los Angeles Police Department Officer Sara Fayden said officers discovered Lam's body Tuesday in the hotel water tank after guests complained of low water pressure.
A Los Angeles County Department of Public Health spokesman said the department was investigating whether the hotel's water supply had been contaminated, though Fire Capt. Jaime Moore said a water sample showed "no biohazard concerns" to hotel guests.
LAPD Sgt. Rudy Lopez said police are investigating how Lam gained access to the rooftop water tank. The tank could be easily opened, but access to the hotel roof is locked and armed with an alarm, KNBC reported.