CHICAGO (WBBM) – A Chicago firefighter suffered a shoulder injury while fighting a 3-11 alarm fire that heavily damaged two apartment buildings in the north side Lakeview neighborhood.

Residents of the three-story, U-shaped brick apartment buildings at 841-49 and 851-59 W. Cornelia Av. were able to escape without injury.

READ MORE: Chicago Weather Alert: Lake-Effect Snow On The Way With 6 To 8 Inches Possible In Some Areas; Winter Storm Warning Issued

LISTEN: WBBM Newsradio’s Bob Roberts Reports

The fire began on a rear wooden stairway shared by the two buildings. Fire officials said the flames spread up the stairway, into the third floor apartments and from there to the space between the ceiling and roof, making the fire more difficult to extinguish.

READ MORE: View Live Radar

The buildings lack any rear exit aside from the area near the stairway. As a result, firefighters had to go around the block if moved from front to back, instead of through the building, wearing them out more quickly and prompting a third alarm.

One resident of the building, named Ivanna, said she did not hear any fire alarm, only a commotion outside her second-floor window. When she looked outside and saw people running half-clothed with their belongings, she dressed, grabbed her wallet and ran outside.

The firefighter was treated for his injury at nearby Illinois Masonic Hospital.

MORE NEWS: Two Men Shot Dead In Car In Ravenswood; Car Goes On To Crash And Catch Fire

Neither of the buildings was deemed habitable by authorities after the fire. The American Red Cross said it would provide temporary shelter for anyone left homeless by the fire.