A fire caused heavy damage to a commercial building in Upper Macungie Township, Lehigh County.

It started around 10 a.m. Sunday at Fitzpatrick Corrugated Packaging and Displays in the 6900 block of Schantz Road.

Crews at the scene say the fire was contained to the inside the building.

There were no injuries. A few firefighters were treated for heat-related illnesses.

The cause of the fire is under investigation.