As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT T1392/16JAN - DURING CLIMB SMOKE AND FUMES IN CABIN COMING FROM AIR CONDITIONING SYSTEM. TURNED OFF PACKS AND RECIRCULATION SWITCH AND BREAKERS. RETURNED TO ORD AND LANDED WITHOUT INCIDENT. FOUND LEFT PACK AIR CYCLE MACHINE LEAKING OIL. REPLACED AIR CYCLE MACHINE FOR LEFT PACK. SYSTEM GROUND CHECKED NORMAL OPERATION.