Authorities had only searched a small part of the two-story building destroyed by the inferno.
The death toll from a fire at a California warehouse where a rave party had been taking place rose to 33 on Sunday, the authorities said.
"The last number we gave out of deceased folks was 30. That's moved up to 33," Sergeant Ray Kelly of the Alameda County Sheriff's Department said at a late afternoon news conference.
Crews had searched 35 to 40 per cent of the two-story building, which was gutted and left unstable by the inferno late Friday night, he added.