As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRIOR TO TAKEOFF, APPLIED POWER AND WHEELWELL FIRE WARNING LIGHT CAME ON. LIGHT WENT OUT WHEN RETURNED TO IDLE, RETURNED TO BLOCKS. ON LEAK CHECK BY MAINTENANCE, APU SUPPLY DUCT BURST. INSTALLED BLOCKING PLATE AND PLACARDED APU INOPERATIVE.