A major cleanup operation has been launched to tackle a 126,000-gallon oil slick off the southern California coast, which has forced beaches to close and prompted officials to warn of “substantial ecological impacts”, according to NBC News.

The slick is approximately 13 square miles in size, the U.S. Coast Guard Los Angeles said in a tweet Saturday. It added that it was 3 miles off the coast of Newport Beach, a small community 35 miles southeast of Los Angeles.

In a separate statement it said that it was working with a number of agencies including the California Department of Fish and Wildlife’s Office of Spill Prevention and Response on the cleanup operation.

Orange County Supervisor Katrina Foley said in a tweet Saturday thatoil had already washed up onto the beachfront of Huntington Beach in Orange County.

“We’ve started to find dead birds & fish washing up on the shore,” she said, adding the location of the leak was about 5 miles off the coast of Huntington Beach and that oil was continuing to spill from a broken pipeline connected to an offshore oil rig.

The USCG said it was working alongside Beta Offshore, which operates three offshore oil platforms in the Beta Field off the California coast.