CHICAGO (CBS) — A truck repair shop collapsed early Monday in the Austin neighborhood, after a fire set off a couple minor explosions.

Firefighters returning from another fire in the Austin neighborhood spotted the blaze around 12:50 a.m. in a factory building near Lake Street and Cicero Avenue.

“At this time, that fire was already very advanced. It was a building approximately 100 by 100 [feet], with a bowstring constructed roof. Again, this is a very dangerous type of building, and the fire was very advanced, so we were in a defensive mode,” Chicago Fire District Chief Dan Cunningham said.

By shortly after 1 a.m., crews called in a 2-11 alarm, bringing about 100 firefighters to the scene, as the fire quickly burned through the roof. A couple explosions were heard inside the building as crews battled the flames.

By 1:20 a.m., the building had completely collapsed, according to the Fire Department.

With temperatures in the single digits overnight, ice quickly formed on the ground as firefighters doused the flames, and a volunteer working to support the firefighters slipped and fell. He was taken away on a stretcher to be checked out.

Firefighters also had to contend with some frozen hydrants in the area.

A neighboring building was evacuated as a precaution, but no injuries were reported.

The fire was extinguished by about 2:15 a.m.

The truck repair shop is located next to the Green Line, which prompted the CTA to shut down service between the Harlem and Conservatory stops for a couple hours. Normal CTA service resumed around 3 a.m.

The cause of the fire was under investigation.