As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3559, CREW REPORTED WHILE DURING PASSENGER BOARDING, PASSENGERS REPORTED SMOKE IN THE AFT PART OF THE CABIN. CREW DETERMINED THAT THE SMOKE WAS POSSIBLY ELECTRICAL IN NATURE. CREW AND PASSENGERS DEBOARDED SAFELY. AIRCRAFT REMOVED FROM SERVICE. PERFORMED EXTENSIVE RUNS, NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.