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Refinery fire probe looks at spark sources

Jason Dearen

In this undated photo released by the U.S. Chemical Safety Board, structural damage is shown after the Chevron refinery fire in Richmond, Calif. Structural engineers have deemed the site of a Chevron refinery fire in the San Francisco Bay area hazardous for human entry after looking at the failed pipe that leaked and sent a towering plume of black smoke into the sky. Federal and state investigators are discussing plans for how to make the Richmond site safe so the faulty pipe can be removed for testing. (AP Photo/U.S. Chemical Safety Board)

RICHMOND, Calif. (AP) -- Investigators probing the cause of a blaze at Chevron's Richmond refinery are looking at heaters and responding emergency vehicles as possible ignition sources for the massive vapor cloud that spewed from an old, leaky pipe.

U.S. Chemical Safety Board investigator Don Holmstrom says refineries like Chevron's have fired heaters that could have provided a spark for the Aug. 6 inferno.

Holmstrom said a responding Chevron fire truck could be another possible source of ignition, since the 150-to-200-foot-high vapor cloud covered a large area.

The blaze knocked an important refinery unit offline, reducing the facility's production and sending thousands of people to hospitals with breathing and eye irritation complaints.

The average price for a gallon of regular on Wednesday in California was $4.09, up from $3.86 Aug. 7.