As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED SMOKE IN THE CABIN DURING ENGINE START. PASSENGERS DEPLANED. SUSPECT SOURCE OF SMOKE TO BE THE AIR START CART. MAINTENANCE OPERATED BOTH AIR CONDITIONING PACKS AND STARTED BOTH ENGINES WITH NO SMOKE GENERATED. MAINTENANCE PERFORMED A BURNOUT OF THE PNEUMATIC HIGH PRESSURE DUCTING IAW AMM AND REPLACED BOTH COALESCER BAGS AS A PRECAUTION. ALL SYSTEMS NORMAL AND ACFT WAS RETURNED TO SERVICE.