As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 4390 THE CREW REPORTED THAT A BANG WAS HEARD BY A PASSENGER NEAR ROW 8-9 AND THE CABIN FILLED WITH A FOG TYPE OF SMOKE THAT NEVER REACHED THE COCKPIT. THE AIRCRAFT LANDED WITHOUT INCIDENT WHERE MAINTENANCE INSPECTED THE AIRCRAFT AND REMOVED AND REPLACED THE NUMBER TWO (#2) ACM AND ACM EXHAUST DUCT, OPERATIONALLY TESTED WITH NO DEFECTS NOTED AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.