What was found
MAF - FLT 839 - EN ROUTE DFW-SAN, APPROX 45 MINS INTO FLT, AFT CABIN F/A REPORTED STRONG SMELL OF SOMETHING BURNING IN AREA NEAR MID-CABIN. AS COCKPIT DOOR WAS OPENED THE SMELL OF HOT ELECTRICAL/HOT PLASTIC BECAME APPARENT ALONG WITH A LIGHT HAZE IN CABIN. INITIATED EMERGENCY DESCENT, PEFORMED CABIN/COCKPIT FIRE/SMOKE CHECKLIST SMOKE REMOVAL. EMERGENCY LANDED AT MAF W/O INCIDENT. SOURCE OF SMELL COULD NOT BE DETERMINED BUT LINGERED IN A/C CABIN FOR ONE HOUR AFTER COMPLETE POWER DOWN. PERFORMED PACK BURN OUT PER MM. REMOVED AND REPLACED BOTH WATER SEPARATOR BAGS, RAN BOTH PACKS FOR 2 HOURS. NO SMELL NOTED, OPERATE ALL OVENS AND ALL LIGHTS WITH NO SMELL OR SMOKE NOTED. CHECKED E/E AND ALL CARGO PITS NO SM