MADISON, Wis. -

A lightning strike is believed to be the cause of a fire that “significantly damaged” some equipment at a Madison sewerage plant Wednesday morning, officials said.

Madison fire crews were sent around 7 a.m. to the Madison Metropolitan Sewerage District headquarters in the 1600 block of Moorland Road after employees saw lightning and started smelling something burning, according to a release.

When crews arrived on scene, they could see flames coming from the protective cover that houses a rooftop pressure release valve and flame arrester, officials said.

Firefighters put out the fire from a safe distance, and then made sure the fire did not spread, according to the release.

The pressure relief valve where the fire happened sits on top of an anaerobic digester that contains 670,000 gallons of solid waste, officials said. The waste produces about 60,000 cubic feet of methane gas per day.

Firefighters and wastewater treatment staff said they were very concerned that an explosion and widespread damage could happen if the fire spread, according to the release.

The treatment facility and a nearby home were evacuated while crews investigated and put out the fire, officials said. The area was deemed safe around 8 a.m.