One firefighter was injured and 13 families displaced when an extra-alarm blaze struck a Berwyn apartment building Saturday.

Firefighters responded at 4:43 p.m. to a 14-unit, 3-story apartment building on the 2800 block of South Ridgeland Avenue in the near west suburb, and the response was raised to a second alarm, said Berwyn Fire Chief Denis O’Halloran.

The injured firefighter was still being treated Saturday night at a local hospital and a condition was not known, but his injuries did not appear to be life-threatening, O’Halloran said. He did not have exact details of the injuries to the firefighter, but said no other injuries were reported.

The 125- by 75-foot building was heavily damaged and left uninhabitable. One unit was vacant but 13 families were displaced, although an exact number of victims was not available.

No cause for the fire had yet been determined, and personnel remained on the scene late Saturday continuing the investigation, including conducting interviews with witnesses and residents.

Berwyn fire personnel were assisted by Berwyn police and emergency response staff, along with firefighters from North Riverside, Stickney, Cicero, Forest Park, Oak Park, River Forest and Broadview.