At about 4:00 A.M. firefighters from Stations 2 and 5 responded to 158 Flax Hill Rd for a reported structure fire.  Upon a perimeter check of the house, a fire was located in the basement of a 3 story wood frame balloon construction.  Firefighters made an aggressive interior attack and extinguished the main body of fire.  Upper floors were checked for extension using a thermal imaging camera.  Smoldering fires were extinguished and the building was ventilated using positive pressure.  The fire is under investigation.