This is an archived article that was published on in 2012, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

Richmond, Calif. • Investigators were looking at how a small, seemingly insignificant leak at one of the country's biggest oil refineries quickly unraveled into an intense fire that sent acrid black smoke into the sky and hundreds of people to hospitals with health complaints.

This latest disruption at Chevron's refinery in this city about 10 miles northwest of San Francisco — one of the West Coast's big refineries — also was expected to affect gasoline prices in the region.

The Richmond refinery produces about 150,000 barrels of gasoline a day — or 16 percent of the region's daily gasoline consumption of 963,000 barrels, said Tom Kloza, chief oil analyst at Oil Price Information Service. With inventories of gasoline in the region already low compared with the rest of the country, pump prices on the West Coast will soon average more than $4 a gallon, Kloza said.

The leak started as a drip at about 4:15 p.m. Monday, officials said. Chevron — which is required to "immediately" notify the public of any gas leak, fire or oil spill, according to state law — did not consider it an immediate danger to residents nearby.

"At that point in time, there really wasn't anything we could advise the community to do," said Mark Ayers, the refinery's fire chief. "We surely wouldn't advise anybody to shelter in place."

The company's engineers began stripping away insulation on the leaky pipe to investigate the source, which released a vapor of a flammable substance similar to diesel. About two and a half hours later, a conflagration had officials scrambling to warn residents to stay inside.

Chevron officials notified Contra Costa County so it could activate its emergency warning system, said Randy Sawyer, director of the county's health services agency.

"We are still trying to determine whether Chevron gave timely notification," Sawyer said.

Richmond's mayor, some residents and community groups have criticized the company's response as too slow, marking the latest conflict between the area's residents and Chevron, which has formally apologized for the fire and polluting smoke. The refinery has been the target of complaints and lawsuits by residents of the mostly low-income community. The area is home to five major oil refineries.

Emotions ran high during a Tuesday night community meeting in Richmond, where hundreds of people heckled a panel of Chevron and local officials.

"I can assure you I have the utmost respect for this community," Nigel Hearne, the general manager of the refinery, said. Police officers lined the stage as the speakers left.

State workplace safety investigators were also investigating the blaze.