The city of Huntington Beach on Saturday night closed ocean waters from the Santa Ana River jetty to the city pier due to an oil spill that the U.S. Coast Guard was investigating earlier in the day, officials said. Oil reached Huntington Beach on Saturday night and was also expected to affect beaches in Newport Beach.

The spill was estimated at 126,000 gallons as of Saturday evening, said Jennifer Carey, a spokesperson for the Huntington Beach Police Department.

The oil made contact with the shore in Huntington Beach, but booms were quickly laid down to block impacts to the wetlands and address ecological concerns, said Carey. Talbert Marsh, off Brookhurst Street and Pacific Coast Highway, was impacted by some oil.

Huntington Beach Mayor Kim Carr described the situation as a “potential ecologic disaster” and said some of the oil also reached the Santa Ana River Trail.

Health officials warned people not to swim, surf or exercise by the beach because of the potential health hazards, including toxic fumes, which also threaten marine life and other wildlife.

The city of Newport Beach also said what it called a “large oil spill” — was expected to come ashore late Saturday between the Balboa Pier and the Corona del Mar Main Beach.

The Coast Guard received initial reports of an oil sheen off the coast of Newport Beach around 9:10 a.m. Saturday. By 12:15 p.m., it was responding to an oil spill about 13 square miles in size, 3 miles off the coast of Newport Beach.

It wasn’t immediately confirmed what caused the spill. Newport Beach City Councilman Will O’Neill posted on social media Saturday evening that the spill was related to a mechanical issue from an oil platform about seven miles offshore from Huntington Beach.

The Coast Guard as of late Saturday had not confirmed the cause of the spill and said it was under investigation.

The Orange County Health Care Agency planned to assess the spill and determine a clean-up plan on Sunday morning, Carey said.

The Newport Beach Fire Department planned to send a rescue boat out toward the site Saturday to get more information on the approximate location, after the crew finished assisting with the Pacific Airshow in Huntington Beach for the day, Battalion Chief Brent Jacobsen said. It was unclear as of late Saturday evening if the airshow on Sunday would be affected by the spill and the spill response.

The Newport Beach department said it had heard secondhand and over boat radios that people had seen an oil spill between three and seven miles off the coast, Jacobsen said.

“We don’t have a complete picture yet,” he said.

Hazardous materials teams were on site to deal with any impacts and provide equipment. Marine safety boats and marine helicopters from Huntington Beach were also deployed.

Officials said public volunteers are not needed and could hinder response efforts. The public was asked to avoid any oiled areas.

“If anyone encounters oiled wildlife, do not approach. Call the Oiled Wildlife Care Network at 1-877-823-6926,” state and federal officials said in a joint statement.

The California Department of Fish and Wildlife, Office of Spill Prevention and Response, Beta Offshore, Long Beach, Newport Beach, Huntington Beach and the Orange County Sheriff’s Department were participating in the response.

City News Service contributed to this story.