As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MSP - FLT 721 - LOG PAGE 867-33, THE CREW REPORTED THAT DURING CLIMB-OUT, NR 3 ENGINE FIRE WARNING ILLUMINATED. THE ACFT RETURNED TO MSP AND LANDED WITHOUT INCIDENT. MAINTENANCE CREW FOUND BROKEN FUEL HEAT DUCT AND ARE CURRENTLY IN THE PROCESS OF REPAIRS. (X) SD; REMOVED AND REPLACED BROKEN FUEL HEAT BLEED AIR DUCT, RAN ENGINE AND NO LEAKS NOTED.