As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED SMOKE IN CABIN AFTER TAKEOFF. THE ACFT RETURNED TO DEPARTURE AND LANDED WITHOUT INCIDENT. MX INSPECTED AND REPLACED THE NR 1 ENGINE. OPS CHECKED GOOD. CAUSE OF SMOKE WAS OIL LEAKING UNDER NR 4 SEAL RUNNER. SB 72-401 INSTALLS A NEW DESIGN SPACER AND HIGHER TEMP CARBON SEALS.