MADISON, Wis. — A communications company says a subcontractor was working "on site" before an explosion that killed a Wisconsin firefighter this week. But it wasn't immediately clear if the subcontractor was responsible for breaking a gas main ahead of the blast.

Verizon Wireless said Thursday it had contracted with Kansas-based Bear Communications for a fiber project in Sun Prairie, a Madison suburb.

Bear said in a statement to WISC-TV that its subcontractor was working "on site" but gave no other details. The company said "many questions" remain and it's cooperating with investigators.

Bear didn't immediately respond to messages from The Associated Press.

The blast Tuesday killed firefighter Cory Barr and devastated the city's downtown area. Authorities have said a leak from a natural gas main struck by a contractor preceded the blast.