As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: SMOKE/FUMES WARNING IN LAVATORY D IN FLIGHT WITH NO APPARENT SOURCE OF SMOKE/FUMES DETECTED. THE WARNING ILLUMINATED FOR APPROXIMATELY 40 SECONDS. MAINTENANCE FOUND THE FILTER ON SMOKE ALARM EXTREMELY DIRTY AND CLEANED IT.