An oil sheen off the coast of Southern California triggered alarms in the state this week before dissipating, however, authorities said that the source of the oil remains a mystery. The news comes nearly a month after the Golden State struggled to mitigate the impact of a major oil spill.

The United States Coast Guard said it had dispatched boats and aircraft over the weekend to probe the oil sheen off the beaches of Orange County, which was reportedly 70 feet by 30 feet, according to reports from Associated Press.

Orange County Register said that the origin of the oil sheen near the coast was not known. Moreover, authorities were also unable to determine where it was first spotted.

Jenna Driscol, California Department of Fish and Wildlife’s liaison officer clarified that As of about 2 PM Saturday, the sheen was no longer visible. United States Coast Guard officials said Saturday night that the sheen had not reappeared and that they would continue monitoring the area.

Also Read: Crude oil spill in California close to 25,000 gallons: US Coast Guard

“It could be nothing, it could be something, but we want to be sure we get an investigation out quickly,” Orange County Supervisor Katrina Foley told the Register on Saturday. She added, “We do not want to repeat what happened last time”, according to reports from Associated Press.

The sheen spotted Saturday was located in the same area where an underwater pipeline owned by Houston-based Amplify Energy leaked up to about 25,000 gallons of crude on October 2. Oil washed ashore, tarring the feathers of dozens of birds and leading to rescues of marine mammals.

The impact of the spill was less than initially feared, but it affected local wetlands and wildlife and shut the shoreline in surf-loving Huntington Beach for a week.

(With AP inputs)