As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EWR INFLIGHT T1883/13FEB - CREW REPORTED SMOKE IN CABIN AFTER TAKEOFF. RETURNED TO EWR AND LANDED WITHOUT INCIDENT. FOUND AUXILLIARY POWER UNIT (APU) LEAKING OIL AT OIL TANK MAGNETIC PLUG. REPLACED O-RINGS ON MAGNETIC PLUG. SYSTEM GROUND CHECKED NORMAL OPERATION.