As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - FLIGHT 2119 - DURING CRUISE FLIGHT, THE CREW RECEIVED A MASTER WARNING WITH ASSOCIATED SMOKE WARNING LIGHT. THIS OCCURRED TWICE DURING FLIGHT, HOWEVER, THE FLIGHT ATTENDANTS DID NOT OBSERVE, OR SMELL, ANY SMOKE. MAINTENANCE INSPECTED THE AIRCRAFT AND THE NR 1 AND NR 2 CARGO SMOKE DETECTORS. DUST WAS OBSERVED ON BOTH. THE DETECTORS WERE CLEANED AND OPERATIONAL CHECKS WERE PERFORMED. THE CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.