Two state agencies have opened separate investigations into Saturday's power plant implosion along Coffee Road that seriously injured one man and hurt several others.
Representatives of Cal-OSHA and the California Public Utilities Commission said their inquiries were under way Monday. Cal-OSHA enforces public and workplace safety laws, while the commission oversees the plant's owner, Pacific Gas and Electric Co.
A Cal-OSHA spokeswoman said her agency's investigation is focusing initially on Alpha Explosives, a Lincoln-based demolition company hired by plant owner PG&E's prime contractor on the job, Cleveland Wrecking Co., of Covina.
"As the investigation progresses, it may become a multiple employer investigation," spokeswoman Erika Monterroza said.
A spokesman for the commission declined to discuss the agency's investigation other than to confirm its existence.
Members of the demolition industry, meanwhile, said several factors likely contributed to the release of shrapnel that peppered spectators and vehicles 1,000 feet east of the plant.
The shrapnel may have escaped because too much explosives -- or the wrong kind -- were used, they said.
Or, the explosives could have been placed incorrectly within the structure -- or the measures used to contain them may have been inadequate, they said.
"When something unusual like this happens, it's a combination of many factors," said Brent Blanchard, director of field operations for Protec Documentation Services, a New Jersey structural blast consulting firm.
"To establish every factor is going to take time, and to speculate about one cause right now would be irresponsible," continued Blanchard, who is also senior editor of the website www.implosionworld.com.
He added that structural changes made to the building could have undermined efforts to contain shrapnel.
"That's not pointing toward negligence," he said. "That typically occurs over decades of a structure's life. Its uses can change."
Mike Taylor, executive director of the National Demolition Association, said demolition companies have different ways of containing shrapnel. Typically, he said, structural columns in buildings set for implosion, are wrapped in a tough fabric that is then surrounded by a chain link fence material.
After that, Taylor said, the column usually gets another layer of strong fabric, and a plywood structure is built around it to contain any shrapnel.
"Usually it tends to be pretty effective containing the shrapnel in these instances," he said.
A PG&E spokesman said Saturday's explosives were handled by Demtech Inc., based in Dubois, Wyo. The firm was hired by Alpha Explosives.
Alpha and Demtech could not be reached for comment Monday. A Cleveland Wrecking spokesman declined to comment.
At least several hundred spectators had gathered early Saturday to watch the implosion of the 1940s-era power plant, which PG&E has not used since 1985.
The detonations occurred about 6 a.m., sending debris eastward over Coffee Road. At least five people were hit, including a Bakersfield man who was flown to a Fresno hospital in critical condition. Others suffered minor injuries.
Saturday's was the second serious accident related to the plant's demolition. On June 19, 2012, a 51-year-old Cleveland Wrecking employee, Luis Roberto Minjarez of Los Angeles, was in an aerial lift making vertical cuts to a large tank when he fell to his death.
Cal-OSHA later determined the tank did not have lateral support, and that Cleveland did not have a permit for the demolition project, among other violations. The agency has levied $20,250 in fines against the company.
PG&E spokesman Denny Boyles said the utility had checked Cleveland's safety record going back three years before hiring the company for the demolition job. He said PG&E left it to Cleveland to check its subcontractors' safety records.
All three contractors on the demolition job have been cited for safety violations within the past decade.
In 2003, OSHA fined Cleveland Wrecking $300 after a worker broke his leg when a piece of ceiling plaster knocked over his 7-foot-tall scaffold.
In 2004, the agency fined Alpha $150 after finding a violation. Details were not available Monday.
OSHA investigators issued a notice of two violations by Demtech in 2010, but no fines were issued. Records state the incident was related to respiratory protection.
-- Staff writer Courtenay Edelhart contributed to this report.