As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MAIN DECK FIRE WARNING. QRH PROCEDURE AND ALL CHECK LISTS ACCOMPLISHED. PERFORMED EMERGENCY RETURN. AIRCRAFT LANDED NORMALLY. VISUAL INSPECTION OF MAIN DECK CARGO COMPARTMENT. NO EVIDENCE OF FIRE & SMOKE. AS PRECAUTION, REPLACED NR 8 LOOP A AND B SMOKE DETECTORS IAW AMM 26-14-01 AND AFOLTS WARNING CARD IAW AMM 26-10-01. ALL SYSTEMS OPERATE NORMALLY.