U.S. safety investigators launched a probe into a Feb. 16 fire at Valero Energy'sMcKee refinery in Sunray, Texas, the U.S. Chemical Safety and Hazard Investigation Board said in a statement.
A Valero spokeswoman said the company is cooperating with the investigation, but would not comment while the probe is underway.
In addition to trying to determine how the propane-fueled fire began at the 170,000 barrel per day refinery 60 miles north of Amarillo, Texas, the CSB will look at how the fire spread to damage chlorine cylinders, threatening to detonate a giant propane storage tank.
"Once the propane was released and ignited, the fire spread rapidly," said the board's lead investigator Jim Lay. "Within minutes, a critical piping rack -- on which some of the support beams had not been fireproofed -- collapsed, breaking open pipes and adding fuel to the blaze."
Refinery workers were unable to shut down pumps that would have cut the flow of hydrocarbon liquids into the fire or set off firewater deluge systems that would have cooled exposed equipment, Lay said in the statement.
"...Effective fireproofing and remote shutdown and deluge system capability are critical for keeping a fire contained and preventing catastrophic impacts on a facility," CSB Chairman Carolyn Merritt said.
The McKee refinery has been shut since the plant's 400 workers were evacuated on the day of the fire. A partial restart is not expected before early April.
One worker remains in a hospital after receiving severe burns in the fire. Two other workers have been released from the hospital after being treated for burns.
Gasoline prices in West Coast markets are elevated in part due to the shutdown of the McKee refinery, which supplies Arizona markets that are also fed by Los Angeles refineries.
The CSB investigates chemical industry accidents to determine their root causes, but has no authority to issue regulations.