A lightning strike is believed to be the cause of a fire that started early Wednesday morning at the Madison Metropolitan Sewerage District headquarters on Madison’s south side.

According to a Madison Fire Department incident report, Ladder Company 6 and other crews arrived on the scene after employees saw lightning and smelled something burning.

Firefighters stopped the fire from a distance.

Firefighters and wastewater treatment staff were concerned an explosion and widespread damage could have happened because the location where the fire occurred sits on top of a digester that contains 670,000 gallons of solid waste. Each day the waste produces 60,000 cubic feet of methane gas.

The wastewater treatment operations building and a nearby home were evacuated. After crews extinguished the fire, the area was deemed safe and crews were cleared from the scene within an hour.