As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE NUMBER THREE ENGINE FIRE WARNING LIGHT ILLUMINATED. DISCHARGED BOTH ENGINE FIRE BOTTLES AND FIRE LIGHT REMAINED ON. RETURNED AIRCRAFT TO AIRPORT. FOUND FIREWALL LOOP TO BE AT FAULT. REMOVED AND REPLACED FIRE LOOP SYSTEM, OPERATIONALLY CHECKS NORMAL.