Smoke clouds covered large portions of the Bay Area in northern California hours after a fire shut down a Chevron oil refinery in the city of Richmond.
Various news outlets reported smoke and flames that could be seen for miles and hundreds of residents sought treatment for respitory problems, complaining of respiratory problems, according to the San Pablo, California-based Doctors Medical Center.
The explosions at the plant -- which produces gasoline, jet fuel, diesel fuel and lubricants, as well as chemicals used to manufacture many other products -- started Monday evening and at least two fires sent thick, black smoke into the sky, The San Francisco Chronicle reported Tuesday.
"I walked outside and saw what looked like a lot of steam coming out of Chevron, way more than usual. I thought they must have blown a boiler," Ryan Lackay, a 45-year-old employee at a chemical plant next door to the refinery, told Reuters.
"And then all of a sudden it just went whoosh, it ignited."
Chevron officials said the fire began at the refinery's No. 4 Crude Unit, according to United Press International. An inspection crew discovered a diesel leak in a line in the unit and the leak was enlarging.