Arson detectives are investigating three separate fires at a federal Superfund site in Port Jefferson Station, a Suffolk County police spokeswoman said Friday.

The first blaze, at an abandoned Willis Avenue house on the former site of Lawrence Aviation Industries, was reported at 12:55 p.m. Thursday, police said. The second fire, which damaged a building on Hulse Road, was reported at 8:50 p.m.

The third fire, at a vacant two-story warehouse off Sheep Pasture Road, was reported at 9:15 p.m. Thursday.

Firefighters were still at the scene after midnight, according to the Suffolk County Department of Fire, Rescue and Emergency Services.

Two firefighters underwent a medical evaluation after battling one of the fires, authorities said. They were not hospitalized.

The Terryville Fire Department directed efforts to put out the blaze at the warehouse. Other departments that responded included Coram, Selden, Mount Sinai and Miller Place, fire officials said. Terryville fire officials could not be reached for comment Friday.

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Authorities have said the 126-acre site was used illegally as a dumping ground for tons of sludge and hazardous waste before the aircraft-parts manufacturer closed in 2003.

The property is being rehabilitated as part of a $27 million cleanup by the U.S. Environmental Protection Agency. Several years ago, the Brookhaven Town Board voted to allow light industrial uses there, such as solar energy panels, once the cleanup is complete, projected for 2035.