RICHMOND, Calif., Sept. 7 (UPI) -- Chevron reported that a flash fire erupted at a unit of at its Richmond, Calif., oil refinery about 10 minutes before a major blaze broke out in August.
Chevron shut one of the units at its Richmond refinery following a fire in early August. Investigators with the U.S. Chemical Safety Board agency said refinery workers were working to stem a leak from an 8-inch line at one of the units at the refinery before the fire started.
Chevron, in an update to regulators, said a small flash fire occurred at an insulated pipe about 10 minutes before the fire. Roughly 5 minutes after the flash fire, operators shut the unit down and a white cloud became visible.
"A significant amount of water was being applied on scene and considerable steam was created," the company said. "Because the white cloud did not ignite we have questions about its composition."
A fireball erupted shortly afterward. The cause of the primary leak and the potential ignition source are under investigation.
The Richmond refinery is the third largest in California. It can process more than 242,000 barrels of oil per day.