As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI IN , SHORTLY AFTER PUTTING ELECTRICS ON APU BUSS, GOT A APU FIRE WARNING STOPPED AIRCRAFT , SET BRAKES AND PERFORMED APU FIRE QRC AND QRH. TAXIED TO GATE. DID BLOW ONE FIRE BOTTLE INTO APU. GROUNDED - YES. OIL SOAKED / LOW OIL IN TANK. SUSPECT APU INTERNAL FAILURE. R&R APU / CLEANED APU DRAIN SHROUD IAW T/C 783490/0. OPS CHK / LEAK CHK GOOD . INSPECTED APU REF B737-700 AMM 49-11-00 FOR INSP AFTER APU POWER PLANT FIRE.