Authorities are trying to find the source of a wide oil slick spotted at San Francisco’s Aquatic Park on Tuesday morning.
The “light rainbow sheen” was called in around 6:30 a.m., U.S. Coast Guard Lt. Laura Williams said.
The sheen “came in on an ebb tide,” she said.
Because it was such a wide sheen, authorities said it was difficult to estimate the amount of pollution. The oil sheen appeared to be evaporating, which is a positive sign, Williams said.
The National Park Service and marine patrol are investigating.