Auburn firefighters spent seven hours Saturday knocking down hot spots in a house fire that broke out at 52 Stevens Mill Road at 5:23 a.m. Platoon Chief Richard McFadden said the house was unoccupied at the time and looked as though it was being refurbished. He estimated damage to the house, a total loss, at $120,000. Owner Carlene Leblonde had insurance, he said. The cause of the fire and where it originated in the home are still under investigation. One firefighter injured his ankle when he fell through the first floor and landed in the basement, McFadden said. He was taken to Central Maine Medical Center, where he was treated and released.