Authorities are investigating Monday the cause of a huge fire that ripped through several businesses in the Midway District. The incident was reported at about 5 p.m. Sunday at Fleet Welding in the 3500 block of Hancock Street. Hazardous material crews were called to the scene and fire crews battled the flames that spread to multiple businesses. By about 6 p.m., crews had contained the fire, though smoke was still seen coming from the area. Motorists could see the intense fire from nearby freeways.