The Suffolk County police arson squad is investigating a Sunday fire at an abandoned building at the Pilgrim Psychiatric Center in Brentwood.
Brentwood fire marshal Rob Kuehn said Monday that the fire was confined to the center's former laundry building.
A police spokeswoman said it was reported about 6:40 p.m. and that it appears criminal in nature.
One firefighter hurt his wrist, Kuehn said. He was treated at Southside Hospital in Bay Shore.
The fire was confined to the interior of the building but it was hard to assess the damage it caused. "It's difficult to tell the extent of the damage because some of the buildings already are in deplorable condition," Kuehn said. "So it's hard to tell what damage was done before the fire and from the fire."
Four fire departments responded: Brentwood, Central Islip, Deer Park and Commack.
The arson squad also is investigating a fire that burned for four hours Wednesday at the former Kings Park Psychiatric Center.
Arson detectives said that fire was intentionally set. State parks police also are investigating.
A police spokeswoman said Monday that there doesn't appear to be any connection between the two fires.