The source of the oil isn't immediately clear, according to the US Coast Guard.
CNN  — 

The source of an oil sheen spotted in the Southern California waters of Huntington Beach late last week appeared to be “lightly weathered crude oil” and not gasoline or diesel, the US Coast Guard said Monday.

The US Coast Guard previously said the sheen was first spotted Thursday. Over the weekend, cleanup crews recovered roughly 85 gallons of oil product from the waters off the coast of Huntington Beach, which is known for its beaches and goes by the moniker Surf City USA. Roughly 1,050 pounds of oily waste, sand and tar balls were also removed from the shoreline, the Coast Guard said.

By Saturday morning, when local officials conducted a helicopter flyover, no oil sheen could be seen, according to a Facebook post from the City of Huntington Beach.

Though examinations of the collected oil samples did not definitively identify its source, preliminary results appeared to show it was consistent with local crude oil – and not crude oil that was imported to California, the Coast Guard said.

“The preliminary laboratory results indicate that the oil samples analyzed from this incident are more characteristic of freshly produced oil than heavily weathered oil, which is associated with typical natural seeps,” it said.

The incident is believed to be a “one-time event,” officials said, adding lifeguards will continue to monitor the beach for “tarball conditions.”

Nearby cities monitored potential impacts

Last week’s oil sheen was about 1/2 mile wide and approximately 2 and 1/2 miles long, the Coast Guard said in an earlier news release. It was spotted about 1 and 1/2 half miles off the coast, the Coast Guard said.

On Friday, about 85% of the total oil sheen was removed “before the deteriorating sea state caused operations to pause for the evening,” the Coast Guard said.

“The oil spill off the coast in HB is contained, protections in place to protect our wetlands & marshes, & investigation & testing are still ongoing,” Orange County Supervisor Katrina Foley said on Friday. “Clean up underway.”

In the search for oiled wildlife, one grebe – an aquatic diving bird – with oil on it was recovered Friday afternoon, according to the Coast Guard.

The nearby cities of Newport Beach, Long Beach and Laguna Beach said in statements they were monitoring any impacts to their shorelines from the oil.

The incident comes a little more than 2 years after a massive spill of as much as 131,000 gallons of oil in the same vicinity prompted officials to close area beaches for about a week.

Amplify Energy, the owner of the oil pipeline involved in the 2021 spill, said on Monday it was “confident that the sheen is not related to our operations.”

“While Amplify reported a minor discharge of produced water from Platform Elly that occurred on the morning of March 8th, U.S. Coast Guard/Unified Command reported over the weekend that, ‘the characteristics of the produced water from Platform Elly do not align with what was observed from the sheen,’” it said.

The company added it was cooperating with the US Coast Guard and other authorities to “provide support in any way we can.”

CNN’s Jack Hannah and Taylor Romine contributed to this report.