What was found
ON FLIGHT 3864 THE CREW REPORTED SMOKE IN AFT CABIN ON APU RESTART. AIRCRAFT CAME FROM DE-ICE PAD. THE AIRCRAFT WAS REMOVED FROM SERVICE. PERFORMED OPERATIONAL CHECK OF APU. ALL PARAMETERS NORMAL. RAN APU AND PACK FOR 1 HOUR, ALL EVIDENCE OF SMOKE AND ODOR DISSIPATED. SUSPECT DE-ICE FLUIID IN APU INLET. NO PARTS REMOVED OR REPLACED. OK FOR SERVICE. THE AIRCRAFT WAS RETURNED TO SERVICE.