An unknown amount of diesel fuel leaked Monday from a lobster boat that sank at its mooring in the Washington County town of Harrington.

The capacity of the Relentless’ diesel fuel tank was 250 gallons, but the Coast Guard and the Maine Department of Environmental Protection, which oversaw the salvage operation, were not certain how much may have leaked into the Pleasant River.

The Coast Guard said in a press release that “some diesel fuel escaped from the tank and was captured by the boom and ultimately removed from the water.”

The Coast Guard said the 42-foot fishing vessel sank at its mooring early Monday morning.

“Any vessel sinking is a serious situation, but fortunately nobody was aboard, and we were able to quickly combine our booming resources from the Coast Guard and DEP to recover the leaked fuel,” said Lt. Tim McNamara, supervisor of the U.S. Coast Guard Marine Safety Detachment in Belfast.

The cause of the sinking remains under investigation.