As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE TO AMS AT APPROXIMATELY 02:45Z, NR 3 AFT CARGO SMOKE DETECTOR LIGHT ILLUMINATED ALONG WITH MASTER WARNING AND CARGO FIRE SUMMARY LIGHT. FOLLOWED COM PROCEDURES, DISCHARGED BOTH FIRE BOTTLES, AND DIVERTED TO KEF. NO EVIDENCE OF FIRE WAS FOUND. MAINTENANCE CHECKED THE WIRING AND REPLACED THE SMOKE DETECTOR. OPERATIONAL CHECK GOOD.