As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HAD APU RUNNING, ACM OVERHEAT ILLUMINATED FOR A SECOND AND WENT OUT, AFTER 15 TO 25 SECONDS SMOKE FILLED THE CABIN AND COCKPIT FROM THE OVERHEAD VENTS. FOUND ACM EXHAUST DUCT ASSY MATERIAL COMING APART AND BLOCKING EXHAUST AIR FLOW. R & R EXHAUST DUCT ASSY. OPS CHECKED GOOD IAW MM CH 21-51-00.