California's Department of Industrial Relations has begun investigating two fatalities at a plastics components plant.
The deaths occurred at Solus Industrial Innovations LLC in Rancho Santa Margarita on March 19.
Two other workers were injured in the incident.
The employees were inspecting a malfunctioning water heater when it exploded at about 11:40 p.m. Only six of Solus' 80 employees at the site were working when the blast occurred.
One news report referred to the heater as a residential type, but Captain Greg McKeown of the Orange County Fire Department simply called it an electric water heater.
The Solus plant makes components, many of them plastic, for conveyor systems. The plant's processes include plastics machining of nylon, ultrahigh-molecular-weight polyethylene, acetal and other thermoplastics into conveyor components. It also does custom plastics machining.
The company also makes extruded plastics, but it is unclear if the company does that in Rancho Santa Margarita. Solus' other U.S. facilities are in Sanford, N.C., and Indianapolis.
Company officials declined to provide manufacturing details for the Rancho Santa Margarita operation.
Solus' parent company, Emerson Power Transmission of St. Louis, issued a statement March 20 expressing condolences and announcing a college fund for children of the deceased employees, but it had no other comment.
The water heater was used in an industrial process, Orange County Battalion Chief Kris Concepcion said by telephone. He could not be more specific.
Emerson acquired Solus late last year along with System Plast SpA of Telgate, Italy. System Plast was a major materials-handling systems supplier with expertise in plastics machining, extrusion and injection molding.
California DIR spokeswoman Erika Monterroza said the investigation into the explosion could take three to four months. The investigation is being handled by DIR's Santa Anna district office.
Following the explosion, the fire department deemed the building unsafe for occupation. Damage, estimated at about $1 million, was confined to the Solus facility.
No hazardous materials alert was issued.