City firefighters rushed to the Health Innovation Center, a four-story medical office building on the UPMC Williamsport campus, when a small fire broke out Monday evening in the heating ventilation and air conditioning unit on the roof, according to Fire Platoon Chief Mark Killian.

The fire at 740 High St. occurred about 5:40 p.m. when a staff member, leaving work for the day, discovered smoke in a pediatric patient care room on the fourth floor, Killian said.

There were no patients in the building at the time as the center was already closed to the public, he added. 911 was called and a fire alarm was pulled.

Hospital security responded and quickly doused the small electrical fire with a portable extinquisher. Firefighters stretched one fire hose across the front of the building in case it was needed, but it did not have to be charged.