Around 9:30 pm Friday evening, San Bernardino County Fire responded to reports of a structure fire on the 1500 block of W. Mills Street. Arriving engines located a commercial building with smoke and fire showing. Crews immediately began a defensive attack on the fire. Firefighters were able to obtain a knock down on the fire within 20 minutes. The cause of the fire in unknown at time time. No injuries have been reported at this time.