As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING GROUND OPERATION OF APU, THE FIRE WARNING ACTIVATED AND THE APU AUTO SHUT DOWN WITH SMOKE COMING OUT OF THE APU SHROUD. INSPECTION FOUND CLAMP BROKEN FOR INNER EXHAUST DUCT AT SPOT WELD. INSPECTED APU, NO OTHER DAMAGE NOTED. REPLACED O-RING AND CLAMP. RUN AND OPS CHECKS GOOD, MM 49-00. (X)