Chicago firefighters were called to a two-alarm building fire near a school on the city's Northwest Side on Friday afternoon.

The Chicago Fire Department said more than 100 firefighters responded to the fire in a multi-unit apartment complex in the 8600 block of West Foster Avenue, not far from O'Hare International Airport, around 2:15 p.m. 

Flames and thick black smoke could be seen coming from the apartment complex. The buildings were evacuated and warming buses were called for the residents.

Firefighters spent hours in frigid temperatures trying to put out flames in the top floors of the apartment complex.

Witnesses said it was a chaotic scene as they raced to get to safety.

"My neighbor, he knocked on my door and tell me, 'There's fire, you have to get out,'" said Olesia Kravchuk, who was among the tenants who evacuated the building. 

One tenant, named Robert, said he was getting out of the shower when he smelled smoke.

"Then I heard sirens, and I looked. It's getting closer and closer and closer. I looked, the Fire Department coming around the corner, and the fireman jumped out of the truck. 'Get out, get out!' He yelled to some people. They were burning over here, and then an older guy and some young girl, they ran out real quick, and then a lot of people, and then they started evacuating everybody," he said.

The complex is also near Dirksen Elementary School, and students and parents were checking out the scene as they left the area after the school day. 

With smoke spreading and fire engines surrounding the area, people spilled out into the street in freezing temperatures as they evacuated, including children and parents leaving Dirksen.

"The kids got out of the building. When we came, people were self-evacuating, but we used the school for rehab," Walker said.

Fire Department officials said four or five units in the building sustained significant damage in the blaze, and part of the building collapsed.

Deputy Commissioner Donald Waker said the fire spread from the walls to the ceiling to the roof, but quick actions by firefighters prevented the blaze from getting any worse.

"It was traveling, and we was able to do a trench cut to keep it from traveling from apartment to apartment, and we was able to save the majority of the building," he said.

No one who lives in the building was injured, but one firefighter suffered minor injuries in a slip-and-fall.

The cause of the fire was under investigation Friday evening.