The explosion blew out the front of 100x100 foot building, turning it into a mass of downed, shattered wooden beams. According to the Southern California Gas Co., someone had tampered with the gas line at the building, which may have led to the explosion.
The explosion blew one man across the street with severe burns. Firefighters could find no heartbeat and initially said he had been killed, but he was later revived at Los Angeles County-USC Medical Center.
Another man who became wedged under a truck during the blast was electrocuted by a downed 34,500-volt power line that had fallen on the vehicle and died at a hospital, fire Capt. Stephen Ruda said.
Authorities did not immediately release the names of the two men.
An urban search-and-rescue team shored up beams and sent in dogs to search for another person after hearing reports that someone might be trapped in the debris. Ruda said the dogs detected nothing. Fire officials said everyone was accounted for.
The cause of the blast remained under investigation, but Ruda said it was suspected that natural gas or an industrial gas may have been leaking and collected overnight in the building then ignited when operations resumed in the morning.
The natural gas supply had been disconnected Thursday because the business was behind on its payments, Southern California Gas Co. spokesman Dennis Lord said.
To keep the gas flowing, someone had rerouted a pipe around the meter and a regulator designed to reduce gas pressure to safe levels.
"By bypassing the gas meter that puts a higher than normal pressure into the building. We don't know the reasons for this tampering but the fact of the matter is it was unauthorized and apparently it resulted in this incident," said Dennis Lord, a spokesman for the Southern California Gas Co.
Lord said the meter may have been tampered with in the last 24 hours.
The spray paint-welding company, J.L. Spray, has four employees and makes metal security fences, doors, windows and gates, said Elizabeth Alvarado, a secretary for the business.
Daniel Ibarra, who works at the building, said he was taking out the trash when the blast hit. The 27-year-old man said he smelled gas when he went into work in the morning.
"I was very lucky," said Ibarra, whose thick black hair was singed on top.
The Associated Press contributed to this story.