As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE REPORT IN AFT GALLEY WITH SMOKE ALARM GOING OFF IN AFT FWD LAVATORY WHILE AT GATE. EVENT OCCURRED RUNNING BOTH PACKS OFF THE AIR START UNIT AS APU IS ON DEFERRAL. SHUT OFF PACKS & SMOKE DISSIPATED. FOUND MELTED PLASTIC DEBRIS IN APU INLET. CLEANED APU INLET AREA OF PLASTIC DEBRIS. REACTIVATED APU. ACP APU BURNOUT. NO SMOKE IN CABIN NOTED AFTER 2 HR BURNOUT.