A good Samaritan driving past a Main Road home in Aquebogue noticed flames late Saturday afternoon and stopped to notify the family inside, Riverhead police said.
About six people and a dog safely evacuated the home after hearing word of the flames, police said.
Riverhead police and about 30 Jamesport Fire Department volunteers responded to the scene about 4:30 p.m., said Chief Duffy Griffiths of the Jamesport Fire Department.
Fire officials determined the flames were likely caused by embers that had blown out of a recently lit fireplace, Chief Griffiths said.
The home sustained minimal damage and no one was hurt, he said.