De Pere Firefighters put out a fire on the rooftop of an industrial building Tuesday morning.
Crews were called to Sustana, 1751 Mathew Dr., just before 4 a.m. They found a fire on the roof of an outbuilding that handles methane gas.
Firefighters put out the fire on the rooftop, but it had extended into the insulation, causing firefighters to overhaul the roof. Meanwhile, safety crews were monitoring for methane gas.
The scene was cleared around 6:20 a.m.
Damage to the building was estimated at $120,000. Investigators are still trying to determine what caused the fire.