A Valley Cottage home was illegally divided into more apartments than allowed, according to Rockland fire authorities.
"It was a legal two-family, but somewhere along the line they added two additional apartments without necessary permits," said Gordon Wren, Jr., director of Rockland County Fire and Emergency Services.
The house—located at 61 Lake Road—is 107-years-old. Eight adults and nine children were displaced by the fire.
According to Clarkstown tax records, the home is owned by Sylvester Almiron, who also holds properties in Central Nyack and New City.
Wren said illegally zoned homes are becoming an "epidemic" in Rockland, and make combating flames and rescuing residents difficult for county firefighters—all of whom are volunteers.
"A fire is dangerous to begin with," Wren said. "But in an illegally converted home, you don't know what you're going to find."
Wren said firefighters are trained to first head into bedrooms, which can be difficult to identify in houses like 61 Lake Road. "You have people living in attics, family rooms," he said.
Monday's blaze began at 9:30 a.m. and cut through several stories of the house; authorities closed off Lake Road for several hours after the fire was extinguished to cart out burned debris.
The fire was caused by a space heater in a first floor bathroom, said Clarkstown Fire Inspector Stephen Ungerleider Tuesday afternoon.
"It appears to have ignited some combustibles," he said.
The fire was originally thought to have started in the basement.
Though the house was illegally zoned, it appears its fire equipment was up to date; the 911 dispatchers heard a smoke alarm trilling in the background during the initial emergency phone call, Wren said.
Residents of the home were temporarily sheltered in Playgarten, a day-care facility across the street, while firefighters hosed down the flames. Later, the American Red Cross stepped in to aid the displaced families, dishing out food, medicine and clothing, and helped to make reservations at local motels.