As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT THE AUXILIARY POWER UNIT WAS STARTED AFTER EXITING THE RUNWAY IN KHLG AND THE APU BLEED SWITCH WAS OPENED. AFTER PARKING THE AIRCRAFT THE CABIN FILLED WITH WHITE SMOKE. THE CREW SHUT DOWN THE APU. MAINTENANCE ISSUED MEL 49-00-1 FOR THE APU AND THE AIRCRAFT WAS RETURNED TO SERVICE.