Pittsburgh Bureau of Fire, Police and EMS responded to a fire alarm activation at 12:40 p.m. in the 3400 block of Forbes Avenue on the University of Pittsburgh campus.

When first responders arrived on scene, employees had evacuated an office building complaining of an irritant from an unknown substance.

Some reported to EMS that, while inside, they were having trouble breathing.

Once outside, EMS tended to six people who said their symptoms immediately subsided when they got into the fresh air. No one was transported to the hospital.

Pittsburgh Bureau of Fire conducted air quality tests which were inconclusive. As a precaution, the building was ventilated before anyone was allowed back inside.

University of Pittsburgh Police are investigating. Any additional inquiries should be directed to University of Pittsburgh Media Relations.