As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE REPORTED BY AIRCRAFT DURING TAXI OUT, DISCHARGED FIRE BOTTLE TO EXTINGUISH. INSPECTED APU AND COMPARTMENT IN ACCORDANCE WITH TROUBLESHOOTING MANUAL 49-00-00-810-848-A, NO DEFECT NOTED. REPLACED FIRE BOTTLE IN ACCORDANCE WITH AMM 26-22-41.