As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) SMOKE IN CABIN DURING FLIGHT, OIL FUMES AND SMOKE ENTERED THE CABIN. EMERGENCY WAS DECLARED AND THE ACFT RETURNED TO THE DEPARTURE POINT FOR AN UNEVENTFUL LANDING. POST FLIGHT INSPECTION FOUND A LEAK ON THE AIRFRAME OIL COOLER BYPASS VALVE WHICH APPARENTLY RESULTED IN OIL ENTERING THE ENGINE INLET. SEALS WERE REPLACED AND THE LEAK WAS RESOLVED.