As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAIL LIGHT ILLUMINATED DURING START. AUX AND MAIN CIRCUIT BREAKERS TRIPPED. SMOKE, FIRED BOTTLE. FOUND APU START CONTACTOR WELDED. COLLARED CIRCUIT BREAKER. R & R APU START CONTACTOR AND SMALL CABLE ASSY, EGT, SWAP HARNESS IAW BULLETIN 49-8. OPS CHECKED GOOD.