The blaze broke out around 10:40 p.m. Tuesday, Nov. 16, at a three-story Riverhead residence located at 46 East 2nd St., said the Suffolk County Police.
The five were found by local firefighters after the fire was extinguished, police said.
Eight fire departments responded to battle the blaze that took several hours to put out.
Riverhead Fire Department Ex-Chief Nicholas Luparella reported that upon arrival units were met with heavy fire in the 7,000-square foot home with multiple people evacuating the fire and reporting others still trapped inside.
Firefighters attempted to gain access, but the third floor quickly collapsed onto the second floor, he said.
After extinguishing the fire, a methodical search was conducted on the third floor, and the victims were located inside the home, Luparella said.
Suffolk County Police Homicide Squad and Arson Section detectives responded to a request from Riverhead Town Police to investigate the fire.
No additional information was immediately available.
This is a developing story. Check back to the Daily Voice for updates.
Click here to follow Daily Voice Mount Vernon and receive free news updates.