As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD - FLIGHT 3293 CREW REPORTED LAV SMOKE WARNING IN FLIGHT, NO SMOKE VISIBLE. CREW FOLLOWED QRH PROCEDURE. IAD MAINTENANCE CLEANED SMOKE DETECTOR SENSOR AND PERFORMED LAV SMOKE FIM TASK 26-14-00. ALL OPERATIONAL CHECKS WERE SATISFACTORY. THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.