(UPI) -- Thousands of Northern California residents were ordered to stay indoors after explosions and fires ripped through Chevron's Richmond, Calif., refinery.
The explosions started Monday evening and at least two fires sent thick, black smoke into the sky, The San Francisco Chronicle reported Tuesday.
The fire has been contained, Chevron said on its Web site.
Chevron officials said the fire began at the refinery's No. 4 Crude Unit. An inspection crew discovered a diesel leak in a line in the unit and the leak was enlarging.
Soon after the crew evacuated the area, the diesel ignited, refinery manager Nigel Hearne said.
"We will not speculate on the cause of this incident," Chevron's Web site statement said.
All employees had been accounted for and there were no fatalities, the Chronicle reported. One refinery worker sustained burns to his wrist and was treated at a clinic at the refinery.
Sirens blared to alert residents to stay indoors, and block windows and doors, to help prevent them from breathing tainted air. Health officials said their main concern was crude oil and diesel fumes.
The Chevron Richmond Refinery is one of the largest refineries in the United States, processing up to 240,000 barrels of crude oil a day, the company's Web site said.
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