As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENGINE FIRE LIGHT ILLUMINATED AFTER TAKEOFF. AIRCRAFT RETURNED TO DTW. MAINTENANCE INSPECTED ENGINE AND FOUND STAGE 5 COMPRESSOR BOROSCOPE PLUG LOOSE IN ENGINE COMPARTMENT. MAINTENANCE REINSTALLED AND TORQUED PLUG, RAN AIRCRAFT AT TAKEOFF POWER FOR 5 MINUTES. ALL CHECKS GOOD.