As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMKE/FUME - PRIOR TO PUSH, CREW REPORTED WHITE HAZY SMOKE AND AN OIL SMELL IN THE CABIN FOLLOWED BY A HARD CLUNK AND AN APU AUTO SHUTDOWN. RAMP REPORTED FLAMES IN APU EXHAUST. FOUND APU CHIP DETECTOR FULL OF METAL AND SUSPECTED APU INTERNAL FAILURE. APU REPLACED. PERFORMED ECS DUCT BURN AND COALESCER BAG REPLACEMENT. OPS CHECKS OK. NO FURTHER SMELL OR ODORS FOUND. RTS.(1551774) (AIRCRAFT GROUNDED)