SAN FRANCISCO - A fire that ignited in an underground natural gas storage area in the San Francisco Bay Area prompted the evacuation of thousands of residents, as Chevron emergency crews worked Thursday to purge gas from a pipeline and prevent an explosion, officials said.
The evacuation order was issued late Wednesday for about 1,400 homes near the pipeline in Bay Point after the fire started. About 4,000 people were affected and were still not allowed to return home by midday Thursday.
Workers spent the night purging natural gas from the pipeline and were injecting nitrogen "which will extinguish the fire" burning in the underground vault, Chevron spokesman Cary Wages told reporters.
The underground fire began inside a Chevron natural gas pipeline vault, where workers access pipeline valves, about an hour after a fire crew had been called to the area and extinguished a nearby grass fire, said Terence Carey, an assistant fire chief for the Contra Costa County Fire Protection District.
It was not clear if the grass fire caused the fire inside the pipeline vault. Chevron officials did not respond to repeated questions sent by email asking for details on gas disruptions to the area and how many people would be affected.
Carey said officials realized very quickly Wednesday night "that there was a high probability of danger" and issued an evacuation order for homes within a half-mile (0.8 kilometer) of the pipeline. Officials went door-to-door to tell people to leave their homes in the suburban area about 40 miles (65 kilometers) east of San Francisco.
KTVU-TV reported that many people slept in their parked cars at a light rail station while others parked and slept in outdoor parking lots. Evacuation centers were opened Thursday.
Officials said they would not lift the evacuation order until the underground fire was extinguished and it was safe for fire officials to examine the area.
In 2010, a Pacific Gas & Electric Co, natural gas pipeline exploded in San Bruno, south of San Francisco, killing eight people and destroying 38 homes. The utility was subsequently convicted by a federal court for violating pipeline safety regulations and fined $1.6 billion.