The victim, in his 50s, was trapped on the second floor of the house on Van Buren Street in Massapequa Park just after 1 a.m.
The blaze started in a living room area on the first flood and quickly spread.
Fire was shooting out the second floor windows when firefighters arrived.
Firefighters attempted to rescue the man, but they were forced back by the intense flames.
Authorities say there are indications that the man was awake and attempting to flee, but could not make it out in time.
There does not appear to have been anyone else in the house at the time of the fire.
The fire is possibly electrical in nature, but does not initially appear to be criminal.
The investigation is ongoing.
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