Washington: Plumes of smoke towered above a Chevron oil refinery in southern California late on Thursday following reports of an explosion, although the company said no one was hurt.

Video clips shared online by residents in El Segundo, a coastal suburb a few miles south of the Los Angeles International Airport, showed a massive fireball rising from the refinery with a loud, extended rumble.

Chevron spokesperson Allison Cook told AFP there were no injuries and that all refinery personnel and contractors had been accounted for.

"Chevron fire department personnel, including emergency responders from the City of El Segundo and Manhattan Beach, are actively responding to an isolated fire inside the Chevron El Segundo Refinery," she said.

El Segundo Mayor Chris Pimentel said earlier that the cause of the fire remained unclear, according to local TV station K-CAL News.

LA County Supervisor Holly Mitchell told the outlet that firefighter crews contained the blaze to one area of the refinery and that residents did not have to evacuate.

"It has been contained and there is no cause for alarm for El Segundo or the surrounding areas," Mitchell said.

California Governor Gavin Newsom "has been briefed on the incident at Chevron's El Segundo refinery in Los Angeles County," his media office said on X.

"Our office is coordinating in real time with local and state agencies to protect the surrounding community and ensure public safety," it said.

The flames died down considerably in the hour after the explosion was first reported around 0430 GMT, according to the Los Angeles Times, but flames and smoke remained visible for miles across the South Bay.

The El Segundo facility is the largest oil refinery on the US West Coast, processing more than 276,000 barrels of crude per day, Chevron said on its website.

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