As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK. EICAS MESSAGE AFT MAIN DECK FIRE . UPON INSPECTION NO IDICATION OF FIRE SUSPECT VISABLE MOISTURE . INSPECTED CABIN AREA FOR POSSIBLE FIRE OR SMOKE DAMAGE AND FOUND NONE PRESENT. SUSPECT HEAVY CONDISATION OF RAIN WATER ON MAIN DECK CARGO AREA. CLEANED ALL WATER VENTILATED AIRCRAFT OPS CHECKED NORMAL.