As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FLAME OBSERVED COMING FROM APU EXHAUST DUCT, NO INDICATION IN COCKPIT. GROUND CREW ACTIVATED REMOTE FIRE EXTINQUISHER SWITCH, DISCHARGING BOTTLES. APU AND COMPARTMENT INSPECTED WITH NO EVIDENCE OF FIRE OR DAMAGE. BOTTLES REPLACED AND AIRCRAFT RETURNED TO SERVICE.