As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT RETURNED TO MSP DUE TO NUMBER 1 ENGINE FIRE INDICATION CREW ACCOMPLISHED QRH PROCEDURES, PULLED FIRE HANDLE AND DISCHARGED FIRE BOTTLE (IFSD). AIRCRAFT LANDED SAFELY. MAINTENANCE FOUND BURNT FERRELS ON LOWER CORE FIRE DETECTOR LOOP ASSEMBLY. REMOVED AND REPLACED DETECTOR LOOPS AND GROMMETS.