Monroeville Fire Companies were dispatched to the box alarm for a reported commercial building on fire just after 4:30 this afternoon. Occupants of the business were reporting a working fire in the dust collector. C-50 arrived on scene and reported moderate smoke and visible fire through an open door on the D/A corner of the building. Truck 4 took a position on the C side and split the crews with the interior crew assisting Engine 51 with access and extinguishment. The exterior crew went to the roof and ventilated via existing sky lights. Units were on scene for approximately 90 minutes.