The Suffolk County Police Arson Squad and Homicide Squad says the fire was started accidentally in the living room.
The Office of the Suffolk County Medical Examiner found the cause of the deaths was a combination of smoke inhalation and thermal burns.
Jennifer McCusker, 41, and her three children, Aidan Tarbell, 7, Ava Jane Mistretta, 2, and her twin brother, Brendan Mistretta, who all lived at the home, were transported to Brookhaven Memorial Hospital Medical Center in East Patchogue where they were pronounced dead.
A neighbor saw flames at 16 Hollywood Drive and called 911 as her two sons attempted to enter the residence at 10:15 p.m. on October 11. The two men, one who is an EMT and one who is a volunteer firefighter, were unable to enter the residence due to smoke and heat.