Firefighters extinguished a roof fire at Nemak in Sheboygan Wednesday night. Fire crews responding to Nemak, 4243 Gateway Drive, just before 11:30 p.m. on Wednesday found flames coming from a vent duct on the roof. The vent stack contained aluminum dust, so water could not be used to extinguish it. Firefighters used a collection of portable CO2 and Dry Chemical extinguishers from their rigs and Nemak to extinguish the fire. The roof construction was corrugated steel with a thick rubber overlay. Firefighters used large rotary saws to cut away the metal roof so that the rubber overlay would not continue to burn from the heat of the vent stack.