As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURN FOR SMOKE IN THE CABIN. CREW DECLARED AN EMERGENCY. FLIGHT LANDED WITHOUT FURTHER INCIDENT. OUTSTATION MX CONFIRMED THAT THE RT PACK SEIZED UP AND PRODUCED SMOKE AND FUMES SMELL. PERFORMED HIGH POWER RUNS WITH CREW AND MAINTENANCE, NO FURTHER DISCREPANCIES WERE FOUND. DEFERRED PER MEL 21-51-01. REMOVED AND REPLACED RT ACM.