As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW TO IAH - AFTER TAKEOFF, WHILE CLIMBING THROUGH 6,000FT, CREW RECEIVED "SMOKE TOILET" MESSAGE. THE FLIGHT ATTENDANT CHECKED THE LAV AND SMELLED SMOKE AND HEARD THE ALARM GOING OFF. THE AIRCRAFT RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. EMERGENCY CREWS INSPECTED THE AIRCRAFT AND FOUND NO SIGNS OF FIRE. MAINTENANCE INSPECTED AIRCRAFT AND RESET THE FIRE DETECTION SYSTEM AND FOUND NO FURTHER FAULTS.