ROCKLAND, Maine — City and state crews were responding Friday morning to a diesel fuel spill in Rockland Harbor.

Responders were still assessing the situation and uncertain of the amount of fuel spilled, but one early estimate was about 50 gallons, according to the Rockland Fire Department. The Maine Department of Environmental Protection dispatched a cleanup response team.

The incident occurred when the owner of a boat that was stored at a marina off Front Street pumped what he thought was water out of the bilge of his boat. The fuel tank had apparently ruptured, however, and had filled the bilge with diesel fuel, according to owner Tom Thompson of Florida, who was watching the efforts to contain the spill.

Thompson said he pumped the bilge onto the grounds of the marina. The fire department said that a storm drain is located near where the boat was stored and the drain dumps directly into the harbor.

The boat owner said he would not have pumped the bilge if he had known it was filled with fuel. He said the boat had been stored there for two years.

Workers from the marina were putting absorbent pads into the water and stretching a boom around where the storm drain discharges into the harbor.

The spill was reported at about 8 a.m.