Crews are working to clean up a petroleum spill in San Francisco Bay near the wharf at Chevron’s oil refinery in Richmond, authorities said Wednesday.

The spill was discovered at 3 p.m. Tuesday when a sheen was observed on the water, according to joint statements from federal, state and local agencies and Chevron.

“A pipeline near the wharf was shut down and the apparent source of the leak has been secured. The line in question is used to transport a variety of oil and products that are returned to the refinery for reprocessing,” the unified command said.

The command said in an update Wednesday afternoon that efforts were still underway to determine the composition and official amount of product that was discharged.

The Bay Area Air Quality Management District said Tuesday it was roughly 600 gallons (2,271 liters) of a petroleum and water mixture.

A helicopter overflight found a sheen stretching from Point Molate to Brooks Island, with the impact centered on Keller Beach.

The unified command statement said booms were deployed to contain or deflect the spill and additional booms were being placed preventatively at sensitive areas but there were no reported impacts at those sites.

No oil-covered animals had been observed but the public was urged to report any oiled wildlife they spot.