Editor's Note: KTLA reports that an off-duty firefighter has lost an arm and a leg in the explosion.
LOS ANGELES — State and city investigators worked at an alternative energy company Wednesday to determine what caused an explosion so powerful it blew two employees out of the building, buckled masonry walls and ripped off most of the roof.
The California Division of Occupational Safety and Health is working with firefighters to figure out what happened Tuesday at Rainbow of Hope in the Sylmar section of Los Angeles.
The two critically injured workers, whose names were not immediately released, were at Providence Holy Cross Medical Center. Another employee was treated at the scene for minor injuries, then taken to a nearby hospital for further evaluation.
The company used pressure vessels and was involved in the extraction of hydrogen from water, but the cause of the 4:20 p.m. blast was still under investigation, Los Angeles Fire Department spokesman Brian Humphrey said.
A similar explosion at an alternative fuel company in Simi Valley in June 2010 killed Tyson Larson, 28, at his family's Realm Industries business. The blast occurred as workers tried to break apart hydrogen and oxygen to generate steam.
Investigators would not say if there were any connections between the businesses, but Los Angeles did contact Ventura County authorities because of the similarities.
The Ventura County Star reported in 2010 that a pressurized container used to heat water exploded accidentally during an apparent attempt to make alternative fuel. It said the company was trying to generate steam to break apart hydrogen and oxygen to generate an alternative fuel.
In 2008, there was an explosion at Realm Industries when it was located in another building. That blast was smaller and there were no serious injuries, authorities said at the time.
Tuesday's explosion blew out a rolling steel door, fractured windows in surrounding buildings and damaged cars in a parking lot next to the building.
Building owner Nick Werth told the Daily News of Los Angeles it was leased by Rainbow of Hope, a company working to develop sustainable clean-water systems for developing countries.
He said he had been assured that research being conducted at the site was safe.
Humphrey said damage estimates were still being calculated.