We Energies utility crews have started restoring service to some of the 500 customers affected by an explosion and fire that occurred late Tuesday on a 4-inch natural gas line in the Sun Prairie suburb of Madison, WI, company spokesman Brian Manthey told NGI.

Manthey said a third-party contractor working for a business in the downtown area struck the line Tuesday evening, causing a leak and prompting an evacuation within a half-mile radius of the incident. We Energies utility crews arrived at the site at around 7 p.m. CT, and the explosion and fire occurred shortly thereafter.

“Multiple” valves and gas lines were shut down in the affected area, a process that took “a few hours” to complete as the intensity of the fire forced utility crews to locate and “clamp off” other gas lines that fed ones in the immediately affected area, Manthey said. Meanwhile, residual gas left in the lines even once they were shut had utility and emergency crews working overnight to ensure no other fires ignited.

Manthey said while crews were working to restore gas service to some customers in the downtown area, those in the immediately affected area would remain without service until emergency officials determined it was safe to do so. One firefighter was killed, another was hospitalized in stable condition and several other emergency officials and civilians were injured in the blast, according to the Sun Prairie Fire Department (SPFD).

We Energies, a subsidiary of the WEC Energy Group that serves portions of Wisconsin and Michigan’s Upper Peninsula, continues to determine the extent of damage and is working with authorities on their investigation into Tuesday evening’s incident, Manthey said.

At least five buildings sustained significant damage, and one or two buildings in the area still had active fires early Wednesday, according to an emergency alert on the SPFD website. One residential property also sustained damage. A full inventory of building conditions has not yet been completed.