AVALON, WI (WTAQ) - A maintenance shop for farm equipment was destroyed in a fire at the Gavilon Grain Elevator in Avalon, near Janesville.

Authorities said Wednesday that the fire was discovered in a corner of the building, close to a rail car that was filled with ammonia.

The blaze was reported about 8 p.m. Tuesday. Highway 140 was closed for a time, and people in 20 nearby homes were evacuated for an hour-and-a-half.

One firefighter injured a knee. About five dozen firefighters from a number of area departments helped battle the blaze.

The cause remains under investigation.