10:20 a.m. RICHMOND -- A fire broke out at an oil refinery Monday morning, burning one employee, sending flames as high as 50 feet into the air and prompting an order for residents to stay indoors, authorities said.

The blaze broke out at about 5:24 a.m. at Chevron's Richmond Refinery, a 2,900-acre facility on San Francisco Bay, said Contra Costa County hazardous materials specialist Maria Duazo.

Emergency sirens started blaring 10 minutes later when the company raised the incident's danger level to the highest category, said Eric Jonnson, another hazardous materials specialist with the county.

The fire was under control by 7 a.m. and the worker's injury was minor, Chevron spokesman Dean O'Hair said.

About 1,200 employees were in the refinery when the fire broke out, but they were cleared to return to their jobs after the blaze was contained to the pump where it started when a seal failed and leaked oil, a plant spokeswoman said.

The pump was being shut down for maintenance at the time, she said.

Residents in nearby neighborhoods received telephone calls alerting them to the emergency starting at about 6 a.m. and were instructed to stay inside with their doors and windows shut to avoid breathing toxic fumes, officials said.

Some area residents complained about the 30-minute time lag between when the blaze broke out and they were notified by phone. A private contractor provides notification services for the county, and officials said they were investigating the delay.

"There was some kind of a mechanical glitch or computer glitch that we are looking into at this point," Jonnson said.

The warning was lifted at 8:45 a.m. after air samples showed no unsafe levels of harmful chemicals from the fire.

"There is nothing to look for anymore," Jonnson said.

Toll booth workers on the nearby San Rafael Bridge were evacuated until 8:30 a.m., though motorists got a free ride into Marin County since the bridge remained open to traffic, Duazo said. Highway patrol officers directed vehicles over the bridge.

Located 19 miles northeast of San Francisco, the refinery is the largest in the Bay Area and is more than 100 years old, according to Chevron's Web site. It has a refining capacity of 240,000 barrels of crude oil per day and a plant spokeswoman said production would not be affected.

Richmond is home to several oil refineries, and toxic releases in the area have been common enough that officials installed 26 sirens to warn of danger and tell residents to go inside.

A March 1999 explosion and fire at the Chevron refinery sent hundreds of residents to hospitals. There was also a fire there in Sept. 2003, but it was too small to trigger the warning system.