A plan for salvaging a sunken barge and an overturned tugboat in southern Lake Huron has been approved and work will begin "at first light" Saturday morning, the U.S. Coast Guard said Friday.

The 110-foot dredging barge and the 38-foot tug were overcome in rough seas early Thursday morning about a mile from the Michigan coast and nearly six miles from the opening to the St. Clair River. No one was hurt.

Joe McCoy, president of MCM Marine Inc., which owns the stricken vessels, said he was optimistic they could be recovered and returned to service.

"Hopefully they can get it done within two weeks to a month," McCoy said. "As far as I know, there should be no severe damage" to the barge and tug.

Officials said it still wasn't clear how much diesel fuel escaped. The Coast Guard said the barge was carrying about 1,500 gallons and the tugboat about 300 gallons. Diving crews plugged all fuel valves and tank vents to prevent more fuel from spilling, the Coast Guard said.

Crews from the Coast Guard's Detroit station flew over the scene twice Friday. They saw a small sheen trailing the sunken vessel but said no fuel was seen along the shore.

Fuel that washed onto beaches the previous day had mostly dissipated, said Kristine Morris, spokeswoman for St. Clair County. It covered a roughly half-mile stretch of privately owned land and part of a public beach in Lakeport, about 65 miles northeast of Detroit.

Eleven beaches in the county were reopened Friday while four remained closed, Morris said.

A strong diesel odor that had led the Coast Guard to advise shoreline residents and visitors to take precautions has faded, she said. And the county's hazardous materials team measured air quality along the waterfront and found no problems.

McCoy told The Associated Press that the 110-foot dredging barge, called the Arthur J, and the 38-foot tug Madison were being pulled Thursday morning with another dredge and tug by the Drummond Islander II, a tow boat.

The Arthur J had completed a harbor dredging job in Manistee and was headed for another at Pointe Mouillee on Lake Erie, he said. All six crew members were on board the Drummond Islander II.

The Coast Guard was continuing to investigate the sinking. McCoy said the only possible cause he knew of was the weather.

"My captain had a fairly decent forecast" before setting out, he said. "Once he got under way, the seas built a little higher than the equipment could handle."

The Arthur J started listing around 2 a.m. Thursday, so the captain steered into shallow water, McCoy said. The barge went down about 4:35 am., while the Madison flipped over. No one was injured.

The vessels were partially submerged in 22 feet of water about a mile from the Michigan coast and nearly six miles north of the entrance to the St. Clair River, which links lakes Huron and Erie.

Marine Pollution Control, the company hired by MCM Marine to handle the cleanup, was gathering debris that washed up on shore, Morris said. There were no reports of harm to wildlife.