Updated at 6:14 a.m. Eastern
(AP) SAN FRANCISCO - A fire at one of the largest refineries in the U.S. spewed thick black smoke over cities in the San Francisco Bay area, sending scores of residents to hospitals complaining of breathing problems early Tuesday.
The blaze at the plant in Richmond, about 10 miles northeast of San Francisco, was contained by late Monday although it was not immediately known when the flames would be extinguished, said company spokeswoman Heather Kulp.
The refinery is the largest producer of base oils on the U.S. West Coast, processing up to 240,000 barrels of crude oil a day, according to the company's website.
Residents said they heard loud blasts around 6:15 p.m., when the fire broke out, although Chevron officials could not confirm those reports.
Daniela Rodriguez told the Contra Costa Times that she heard a "big boom" about the time the fire started. The 23-year-old resident said about an hour passed before she received an automated call from the county to remain indoors.
"I was feeling kind of nauseous and light-headed (from the smell)," she told the newspaper.
The Chevron Richmond Refinery makes high-quality products that include gasoline, jet fuel, diesel fuel and lubricants, as well as chemicals used to manufacture many other useful products.
A diesel leak at the refinery's No. 4 Crude Unit ignited shortly after crews were evacuated from the area, Nigel Hearne, manager of the refinery, told The San Francisco Chronicle. Flames shot out from at least two refinery stacks and black smoke continued to pour from the facility early Tuesday.
One employee suffered a minor injury and was receiving first aid, Chevron officials said.
County health officials used automated calls to warn residents of Richmond, San Pablo and the unincorporated community of North Richmond to "shelter in place," meaning they should not only stay inside, but should also turn off heaters, air conditioners and fans, and to cover cracks around doors with tape or damp towels.
A fire at the refinery in January 2007 injured two workers and spewed low levels of sulfur dioxide and other toxins into the air. County officials said then that it was not enough to harm the health of nearby residents.