The clean-up could take some time in the San Francisco Bay near Point Richmond, where hundreds of gallons of petroleum and water mixture from the Chevron Refinery spilled into the water Tuesday afternoon.
The incident started shortly before 3 p.m. Tuesday, according to the facility.
Officials said a boom was placed in the water in the area surrounding the leak, part of an effort to stop the spread.
"We understand that the source is no longer pouring out into the bay, but there is product in the bay," Contra Costa County Hazardous Materials Specialist Maria Dulazo told KCBS Radio. The Bay Area Air Quality District said late Tuesday an estimated 600 gallons of petroleum and water mixture leaked.
That number has not been confirmed by the refinery.
The cause was not immediately known.
There were reports Tuesday afternoon of oil spotted in the water from the wharf south to Keller Beach and possible petroleum "on the shoreline," according to Dulazo. "For the general public, because it's so cool right now, we're not getting a lot of odors," Dulazo said of the smell in the area. "We have people monitoring the shoreline right now and we're getting slight odors at this point in time, but we're not getting overpowering odor report at this point in time."