As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 901 ORD TO YIP - PILOT RETURNED TO FIELD DUE TO LAV SMOKE INDICATION ON CLIMB-OUT. PILOT RPTS RECEIVED TRIPLE CHIME, MASTER CAUTION AND LAV SMOKE. FLT ATTENDANT DID NOT SEE OR SMELL SMOKE. MX PERFORMED LAV SMOKE INSPECTIONS AND PERFORMED ENGINE RUNS WITH NO DEFECTS NOTED.