As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PRE-START & GROUND LOADING, RECEIVED WORD OF A SUSPECTED APU FIRE. FIRED BOTH BOTTLES. APU RUNNING AT FULL POWER. AFTER AUTO SHUTDOWN BLACK SMOKE SEEN COMING FROM APU TAIL PIPE. PERFORMED INSPECTION OF APU BAY WITH NO DEFECTS NOTED. NO EVIDENCE OF FIRE.