As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 1 ENGINE FIRE WARNING LIGHT AND TONE CAME ON MOMENTARILY. NO SECONDARY INDICATIONS. THIS OCCURRED 2 MORE TIMES IN A SPAN OF 3 MINUTES. TURNED TO RETURN TO DEPARTURE WITH NO FURTHER INDICATIONS. INSPECTED NR 1 ENGINE FOR EVIDENCE OF FIRE. NO EVIDENCE OF FIRE FOUND. R & R NR 1 ENGINE AFT OTBD FLAME DETECTOR.