Authorities say a firefighter has been injured while battling a blaze at a north Phoenix commercial building. Phoenix Fire Department officials say the fire captain suffered a back injury and was taken to a hospital by ambulance. They say the firefighter is expected to be discharged later Sunday. His name hasn't been released yet. Fire officials say about 40 firefighters put out the blaze that broke out about 2 a.m. Sunday at a building that contained used restaurant equipment. They say the cause of the fire is under investigation.