U.S. Coast Guard investigators are trying to determine the source of an oil spill that soiled a Lake Huron beach at Cheboygan State Park.
The spill was reported Tuesday afternoon, and cleanup crews were on the scene Wednesday.
Oil covered a section of beach measuring about 25 yards by 300 yards. A sheen estimated at 5 yards by 300 yards was drifting offshore in Duncan Bay.
Coast Guard Petty Officer George Degener says the spill wasn't getting any bigger.
A tugboat and a carferry were in the area, one anchored and the other aground.
Investigators were planning to take samples from both to determine if the oil came from either.
The Coast Guard says park rangers have closed affected sections of the beach for public safety.