As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAX - INFLIGHT DURING CLIMBOUT AT 4000 MEAN SEA LEVEL, LEFT ENGINE FIRE WARNING LIGHT ILLUMINATED. QUICK REFERENCE HANDBOOK PROCEDURES COMPLETED. SHUT DOWN ENGINE. NO BOTTLE FIRED. RETURNED TO LAX AND LANDED SINGLE ENGINE LANDING WITHOUT INCIDENT. FOUND DUCT SECTION LOOSE IN LEFT HAND COWL. REPLACED ANTI ICE DUCT ON LEFT HAND ENGINE UPPER COWL.