A diesel oil spill in the waters near Keyport is dissipating after local and state officials responded to the call Thursday.

At an unknown time Wednesday night, a 32-foot wooden tug boat sank at berth in a private marina at the end of Grandview Boulevard. The docks are near Keyport’s public marina.

The Poulsbo Fire Department first responded Thursday morning, deploying containment booms provided by area spill response trailers from the Department of Ecology. DOE Spokesperson Larry Altose said several trailers were placed around the area two years ago for situations like this. Trailers from Bainbridge Island and Kingston also were brought to the scene.

The sunken boat was submerged in 12-13 feet of water and held two 60-gallon diesel tanks, both of which were nearly empty, according to DOE.

The exact amount of fuel spilled isn’t known.

Poulsbo Fire, the DOE and the U.S. Coast Guard were onsite, assessing the spill and placing absorption pads to sop up oil at the water’s surface. Staff from PM Boatworks of Keyport also assisted, as did U.S. Naval environmental specialists. The specialists searched for spill impacts along area shorelines. The dock where the boat was berthed and the Keystone Beach were determined to be the only areas affected.

A small amount of oil floated beyond the containment boom, forming a widespread layer too thin to recover from the water. At one point, the sheen covered an area estimated at 1,000 feet by 1,000 feet. The DOE reported that sheen is breaking up and evaporating.

The Coast Guard has opened the federal Oil Spill Liability Trust Fund to hire a spill-response contractor, who will continue to remove oil from the water within the containment boom and clean oil from the pier pilings.

The vessel’s owner will have the boat lifted out of the water. There have not yet been reports of harm to wildlife.

The cause of the sinking is under investigation. The DOE’s emergency response trailers will be restocked.