Crews continued Saturday night to drain a "huge amount" of water from the scene of a $10-million industrial fire where several bodies may be buried in the rubble, fire officials said.
"We have a suspicion of three to seven bodies in the rubble, of people who have not been accounted for," Division Chief Bill Shaughnessy of the San Francisco Fire Department said.
The big fire that started with an explosion Friday afternoon destroyed a three-story building and injured 22 people, three critically, before it was controlled by 150 firefighters.
"Some people are sure there were a couple of people in one section of the building who didn't get out of there," Shaughnessy said.
"There's a huge amount of water we have got to get out of there before we can get to the bottom of that rubble," Shaughnessy said. "The water is four feet deep over a 200- by 300-foot area.
"The place just burned to the ground--all you can see is water and some 12-by-12 beams sticking up. The crews will be out there through the night."
There were no known fatalities in the blaze, which began with an explosion that blew the roof off the Bayview Industrial Park building and spread over two adjacent city blocks.
Of the 22 people injured, 17 were still in hospitals. It was not known exactly how many people were in the building when the fire broke out.
Investigators said seven people were unaccounted for after a door-to-door check of the neighborhood, a check of license plates on cars left in the area and talks with survivors.
"It's going to take days to resolve how many people were in the building at the time of the fire and how many people got out," said Fire Investigator Joe Kennedy.
The cause of the blast was not determined, but survivors said welding was taking place in one part of the building when the blast occurred at 3:20 p.m.
The building contained a small paint manufacturer, numerous woodworking shops, auto repair places, artist studios where flammable materials are used, and even some residential units.
The converted tannery building occupied an entire block in the industrial Hunters Point neighborhood near Candlestick Park. Several structures nearby were damaged.
Dr. Ronald Dieckmann, chief of emergency treatment at San Francisco General Hospital, said some of the injured had lung damage from breathing searing smoke containing toxic chemicals.
"Several victims arrived here very close to death and required major resuscitation efforts," he said.