The U.S. Coast Guard says air crews have spotted an oil sheen on Lake Huron during salvage operations for a barge and tugboat that sank in rough weather.

Salvage operations began Saturday in the water off Lakeport for the 110-foot dredging barge and the 38-foot tug. They sank Thursday about a mile from shore.

The Coast Guard says four St. Clair County beaches were closed Saturday because of the leak.

The Coast Guard says the first attempts at raising the barge failed because of its weight. It says crews welded a steel plate over a hole in the side of the tug and refloated it.

The Coast Guard says it's working with ship operator MCM Marine to clean up the oil. Some oil reached shore after the sinking.