Firemen pulled one charred body from the smoking rubble of a San Francisco industrial park building and continued to look for as many as six others. The victim was not identified. Meanwhile, federal agents joined the investigation of the explosion and fire that consumed the block-long building Friday. Frank Sanders, a member of a federal Bureau of Alcohol, Tobacco and Firearms task force helping with the investigation, said agents were checking a report that the blast was accidentally triggered when a spark ignited lacquer from a high-pressure sprayer being used in a carpentry shop. Fire officials said 7 million gallons of water was sprayed onto the fire that injured at least 20 people and left the three-story Bayview Industrial Park a pile of charred debris. Damage was estimated at $10 million to the complex, which contained 126 small businesses. Deputy Fire Chief Richard Crispen said the search for bodies would continue today.