As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FLIGHT CREW REPORTED FUMES IN THE CABIN DURING FLIGHT. (AIRCRAFT OPERATING ON NR 1 PACK - NR 2 PACK INOPERATIVE ON MEL.) AIRCRAFT RETURNED WITH PACKS OFF. POST-FLIGHT INSPECTION FOUND NR 4 ENGINE NR 1 SEAL LEAKING, CONTAMINATING THE CABIN AIR SUPPLY. NR 4 ENGINE WAS REPLACED.