The fire broke out in the evening in the 3000 block of West Madison Street.
The roof of a three-story building was fully engulfed in flames, CFD said.
At least two people were injured, fire officials said.
A large response and over 100 firefighters were called to the scene due the large size of the fire.
"It was big and wide. That stayed like that for a long time," nearby resident Donald Johnson said.
As firefighters beat back the flames, fire eventually pushed into an area between the ceiling and rood, creating unsafe conditions for the first responders.
'So because of that we had to go defensive meaning we pulled all of our firefighters out of the building," CFD District Chief Scott Shawaluk said. "While we were doing that there were several residents inside the building. Some of them were elderly, and we assisted them out of the building some needed medical attention."
One person was rushed to the hospital in critical condition and another person was in serious condition, CFD.
A woman, who did not want to be identified, was nostalgic about the apartment complex she once called home as flames devoured the building.
"We've had a lot of loss over here in the neighborhood in that building," she said. "My neighbor on the second floor was a victim in the E2 tragedy. My brother who's a rapper filmed his first video in front of this building which my grandmother was featured in who's now passed on."
No firefighters were hurt and no other injuries were reported. Fire officials didn't say if the building had working smoke detectors.
Because of the fire, several resident were displaced. The cause of the fire was still under investigation.
No further information was available.