As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3864 THE CREW REPORTED SMOKE IN AFT CABIN ON APU RESTART. THE AIRCRAFT CAME FROM THE DE-ICE PAD. THE AIRCRAFT WAS REMOVED FROM SERVICE. PERFORMED OPERATIONAL CHECK OF THE APU. ALL PARAMETERS WERE NORMAL. RAN APU AND PACK FOR 1 HOUR, ALL EVIDENCE OF SMOKE AND ODOR DISSIPATED. SUSPECT DE-ICE FLUID IN APU INLET. OK FOR SERVICE. THE AIRCRAFT WAS RETURNED TO SERVICE.