The US Coast Guard told the Associated Press that the ship became grounded at about 3am Wednesday on the St Marys River near Sault Ste Marie and was freed and refloated about 6.20am Thursday morning.
Officials for the agency said the Paul R Tregurtha, owned by Ohio-based Interlake Shipping, was carrying about 62,000 tons of coal.
The freighter did block traffic on the outbound channel of the river. Local newspaper the Evening News reported an 11-vessel backup headed for Lake Huron but added no ships destined for Lake Superior were impacted.
The USCG told the AP neither the cargo hold nor fuel system were punctured in the grounding.
