CARIBOU (AP) – A faulty float switch caused a leak of 4,000 to 5,000 gallons of fuel oil at a WPS New England Generation power plant, with some of the spill flowing into the Aroostook River, the company said Tuesday.

Three oil containment booms were placed in the river as crews worked through the day to clean up the spill, said Scott Johnson, a spokesman for the company. Officials from the state Department of Environmental Protection were on the scene.

The accident occurred sometime between 8 p.m. Monday and 6 a.m. Tuesday, according to Johnson, who said the switch failure caused an oil pump to run continuously until the tank overflowed.

The fuel oil spilled onto the pavement and across an earthen berm, with some of it flowing into the river, he said.

WPS New England Generation, which produces electricity for customers in northern Maine, is a subsidiary of WPS Resources Corp. of Green Bay, Wis.