HUNTINGTON BEACH, Calif. (AP) — No recoverable oil remains in the water after a sheen was reported off the Southern California coast, but the cause remains unclear, officials said Saturday.

Authorities detected the 2.5-mile (4-kilometer) long oil sheen Friday morning. Crews recovered about 85% of it, roughly 85 gallons (322 liters), on Friday.

By the time responders conducted flights over the area Saturday, they could no longer see any recoverable sheen, the Coast Guard and Huntington Beach officials said in written statements.

There were some clumps of tar along the beach but not enough to warrant a closure, and there did not appear to be any public health threat from consuming fish from the area, authorities said.

The Coast Guard said three live birds — a cormorant, a loon and a grebe — were found sullied with oil and are being treated.

Authorities had said there were no reports of spills or leaks from oil platforms operating offshore and the sheen did not appear to be growing, which lead them to suspect it was a one-time discharge or natural seepage of oil in the ocean, which are fairly common.

Local officials were paying close attention to the reports following a 2021 leak in an offshore pipeline that sent blobs of crude oil washing ashore in Huntington Beach, a surf-friendly city about 30 miles (48 kilometers) southeast of Los Angeles.