Officials say firefighters responded to Albemarle Avenue in Hempstead about 6 p.m. Saturday to put out the blaze.
After the flames were extinguished, firefighters found a man's body. Officials say the victim was pronounced dead at the scene.
"It is a vacant property, so we had a neighbor state that he saw the fire and called the fire into us," Hempstead Fire Department Chief James Joyce said.
The homicide and arson bomb squad detectives are investigating. Officials have not released the identity of the man.
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