As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PUSH-BACK, CREW HAD AN APU FIRE WARNING INDICATION. 08-31-07 REPLACED APU. ALSO, ACCOMPLISHED APU FIRE EXTINQUISHUNG BOTTLE REPLACEMENT PER MM 26-22-01-401. SUSPECT INTERNAL APU FAILURE: SYMPTOMS CONSISTENT WITH T1 BLADE FAILURE.