As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING APPROACH OF FLT NR 7678 TO ORD FROM FSD CREW REPORTED A LAVATORY SMOKE DETECTOR SOUNDING AND SMOKE IN THE CABIN. CREW COMPLETED LAVATORY SMOKE QRH AND SMOKE DISSIPATED. NO EMERGENCY WAS DECLARED AND FLIGHT LANDED UNEVENTFULLY. THE LAVATORY FAN WAS FOUND TO BE CAUSING THE SMOKE AND WAS REPLACED. AIRCRAFT WAS RELEASED FOR CONTINUED SERVICE.