AERIAL VIEW of oil sheen spotted off the Huntington Beach coast, first spotted on Thursday evening (United States Coast Guard photo).

The cleanup of the oil sheen off the Huntington Beach coastline has been completed. It appears that the petroleum that washed up tar balls on the shore and killed at least sea birds was not an oil leak from a tanker ship, oil platforms or a damaged pipeline.

According to the United States Coast Guard, analysis of the petroleum showed it was “lightly weathered crude oil and not a refined product.” It was, instead, more closely associated with “typical natural seeps.”

Cleanup crews over the weekend were able to recover about 85 gallons of “product” and removed about 1,050 pounds of oily waste and tarballs. The total amount is considered likely to rise.

The oil sheen – first spotted on Thursday afternoon – has been deemed “a one-time event,” but agencies such as the Coast Guard, California Department of Fish and Wildlife and Huntington Beach lifeguards will continue to monitor the area.

“In the face of this environmental challenge, the strength of our partnerships has once again proven to be our greatest asset,” said Capt. Ryan Manning, the federal on-scene coordinator for the response. “As we conclude this response, we remain vigilant and prepared to respond to future incidents, ensuring the protection of our marine and coastal resources for generations to come.”