No one was aboard the Hammond Bay, which went down in the waterway between Michigan's Upper Peninsula and Canada, the U.S. Coast Guard said. The Army Corps is working on a salvage plan for the boat, which is in about 37 feet of water.
"The Coast Guard is enforcing a 500 foot safety zone around the sunken tug," the agency said in a statement.
The Coast Guard said it was notified early Monday that the crew of the Army Corps' tug boat Bill Maier, which was towing three barges and the Hammond Bay, lost sight of the Hammond Bay. The crew found an oil sheen on the water and a Hammond Bay life ring.
The Army Corps vessel Bufe later found the Hammond Bay in the area. The Coast Guard says river traffic is taking place on the river, which runs along Sault Ste. Marie, except for the safety zone around the sunken tug.
According to the Army Corps, the Hammond Bay had 200 gallons of diesel fuel and 15 gallons of oil aboard. The U.S. Coast Guard is surveying the area via helicopter, and said no pollution has been observed from the sunken boat. More monitoring is planned.
"The Coast Guard is working with the Army Corps and other partners to minimize any environmental damage and impact to waterways that the sunken tug may present," the Coast Guard said.