The Pittsburgh Bureau of Fire responded to 911 calls for a commercial fire at 5 Market Square Downtown just before 12 p.m.

The initial response was for a 2-alarm fire that quickly grew to 4 alarms. Buildings immediately adjacent to 5 Market Square were evacuated immediately.

One firefighter, a Lieutenant from 4 Engine, suffered heat exhaustion while fighting the fire. He was transported by EMS to UPMC Mercy Hospital for observation. He was alert and conscious and had exited the structure on his own before being taken to the hospital.

Assistant Fire Chief Norman Auvil said the fire was on the second and third floors of the structure, as well as the roof, when firefighters arrived on scene.

Firefighters were able to gain control of the blaze in less than an hour.

“It was a fast attack, a quick knock-down and good aerial placement by truck company Number 4,” said Auvil.

Pittsburgh Bureau of Police officers from Zone 2 provided support to control traffic and crowds in Market Square during the busy lunch hour as Fire battled the blaze.

The Fire Investigation Unit, which consists of detectives from the Pittsburgh Bureau of Fire as well as the Pittsburgh Bureau of Police, is investigating the exact cause of the fire.