What was found
AS THE AIRCRAFT WAS IN LINE FOR TAKEOFF, THERE WAS REPORT OF AN APU FIRE FROM THE AIRCRAFT BEHIND US. THE APU HAD BEEN SHUT OFF FOR ABOUT 3 MINUTES. THE APU FIRE BOTTLE WAS DISCHARGED ALTHOUGH THERE WAS NEVER ANY FIRE INDICATION IN FLIGHT DECK. FIRE DEPARTMENT RESPONDED AND CONFIRMED NO FLAMES - FOLLOWED AIRCRAFT BACK TO GATE. VENDOR TEARDOWN REPORTS FOR APU FUEL CONTROL UNIT AND FUEL FLOW DIVIDER BOTH INDICATED 'NO FAULT FOUND'. NO SUBSEQUENT EVENTS REPORTED ON THIS AIRCRAFT.