An explosion and fire ripped through a gasoline processing unit at an Exxon Mobil refinery in Torrance, California, near Los Angeles on Wednesday, slightly injuring four workers and shattering windows of surrounding buildings, authorities said.



Exxon confirmed that there had been an "incident" at the refinery but it did not offer further details. It said emergency procedures had been activated to address the situation, and employees were working with the appropriate agencies. Four contractors were taken to a local hospital for evaluation for minor injuries, Exxon said in a statement.

The Division of Occupational Safety and Health, commonly refereed to as Cal/OSHA, is investigating the blast and said it was too early to determine the cause. The agency has issued a temporary order prohibiting work at the unit until inspectors could determine the cause of the explosion, according to NBC News.

The refinery, which employs some 650 employees and uses 550 contractors, produces a specially formulated low-emissions gas that's sold in Southern California, Arizona and Nevada. The site produces nearly 10 percent of all gasoline sold in California, according to Exxon.



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The price of March-delivery CARBOB gasoline in the Los Angeles wholesale market jumped on the news, traders said.



March CARBOB gasoline, which is mandated by the California Air Resources Board, was trading 16 cents a gallon over March RBOB futures on the New York Mercantile Exchange, up 8 cents from Tuesday's close.

Former Shell Oil President John Hofmeister said Exxon is famous for its focus on safety and California "focuses intently" on companies following regulations, but of course incidents still happen.

With respect to prices and supply, California is an island unto itself, so a 10 percent facility could impose a "pretty significant impact if this is going to impact gasoline production," Hofmeister said.

"California produces what it sells. It's a rather thin market because of the environmental conditions placed upon the mix of gasoline that's produced."