A two-family house at 7 Sherman St. in Spring Valley burned down and left three families homeless, in a property being investigated as a possible illegal boarding house that had previously been cited for non-working smoke detectors.

According to the village’s part-time assistant fire inspector, the fire started near the boiler on a Sunday morning, and for several hours tenants didn’t realize it had been smoldering — some simply opened windows to clear the smoke, which even a passing police officer initially mistook for a lawnmower. The inspector said six people lived upstairs and nine lived downstairs, including five children, with tenants paying rent for individual rooms.

About 60 firefighters responded and found heavy flames spreading quickly from the garage up through both floors on one side of the wood-sided building. No one was reported injured. The Red Cross provided emergency lodging to two of the three displaced families.