MILWAUKEE, WI (CBS 58) -- The Milwaukee Fire Department responded to an alarm sounding at a north side auto repair shop early Saturday morning.   The alarm was sounded around 6:40 AM and when firefighters arrived at the repair shop on W Flagg Avenue near N 91^st Street they saw smoking coming from the building.  The fire was quickly put under control and firefighters remained on the scene for about an hour.   The cause of the fire is under investigation.   No estimate of the amount of damage to the building is available at this time.