As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF NR 3 ENGINE FIRE WARNING WENT OFF. EMERGENCY CHECK LIST ACCOMPLISHED. WHEN NR 3 THROTTLE WAS RETARDED FIRE WARNING LIGHT WENT OUT. RETURNED TO AIRPORT. FOUND NR 3 ENGINE ANTI-ICE DUCT BROKEN. REMOVED AND REPLACED NR3 ENGINE ANTI-ICE DUCT IAW MM. OPS CHECKED GOOD.