As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT CREW REPORTED THAT THE LAV SMOKE DETECTOR SOUNDED WITH NO SIGNS OF SMOKE. CREW DECLARED AN EMERGENCY AND RETURN TO DEPARTURE WHERE THEY LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED LAV FOR SIGNS OF SMOKE AND FIRE DAMAGE. MAINTENANCE PERFORMED FIM AND LAV SMOKE DETECTOR SYS TEST IAW AMM AND OPS CHECKED GOOD. MAINTENANCE BELIEVES A PASSENGER WAS SMOKING IN LAV.