The fire broke out at a truck and trailer repair shop at West 41st Street and South Oakley Avenue in the Brighton Park neighborhood.
Video from residents shows just how massive the fire was when it started just before 7 p.m.
"When we were walking we saw some sort of lightning. It was like an explosion, kind of, and it was light, so we're like, 'Oh, this is probably serious,'" said Naomi Sampson, who lives nearby.
Large fire breaks out at SW Side warehouse
The fire department confirmed that some propane tanks inside the business exploded. The tanks and other flammable materials made conditions more difficult for firefighters as they dealt with water pressure issues.
"When our companies reported on the scene, they had heavy fire blowing out the roof. We had a collapse, and we had some explosions," said CFD Assistant Deputy Fire Commissioner Donald Walker. "We had water problems feeding our master streams, and that's what took us so long to put out the fire."
CFD provides update on large Brighton Park fire
CFD said more than 120 department members responded to the scene.
Crews worked for hours to contain the fire while traffic was backed up for about 1 mile at one point as police had to shut down Western Avenue between 41st and 44th streets.
Firefighters extinguished the blaze by 8:30 p.m.
No one was inside the building when the fire broke out, and there have been no reports of injuries, CFD said.
The cause of the fire is still being investigated. Further information was not immediately available.