As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING APU MAINTENANCE BETWEEN FLIGHTS, AN APU COMPARTMENT FIRE WAS REPORTED. NR 1 AIRCRAFT FIRE BOTTLE WAS DISCHARGED AND THE FIRE WAS EXTINGUISHED. MAINTENANCE REMOVED THE APU AND INSPECTED APU COMPARTMENT FINDING NO DAMAGE. REPLACED THE APU AND NR 1 FIRE BOTTLE.