At 5:28 Watertown Fire Rescue responded to roof on fire at 122 Cessna Street. Embers from a smelting furnace may have started a roof decking fire. Plant personnel seen light smoke coming from under the flashing cap on the roofs edge. Upon investigation a smoldering fire had crept through the "buffalo board" into the polystyrene foam underneath the rubber roofing and several inches of ice and snow. Crews punctured  the roof and extinguished the flames with a ABC extinguisher and roof was peeled back to find hidden fires, and to expose a clean edge to help ensure the fire was completely extinguished. Overall roof material removed was about a 14' x 5' feet of doubled roofing on top of metal roof decking.