As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT TAKEOFF, THE NR1 ENGINE FIRE LIGHT ILLUMINATED. THE ACFT RETURNED TO LANDING ZONE WITHOUT INCIDENT. UPON INSP, IT WAS FOUND THAT THE NR 1 ENGINE INBD EXHAUST STACK HAD COME LOOSE FROM THE TURBINE EXHAUST COLLECTOR AND HAD WEDGED ITSELF INTO THE ENGINE COWLING. THE EXHAUST GASSES THEN FORCED ITSELF THRU THE ENGINE COMPARTMENT CAUSING SCORCHING OF ELECTRICAL WIRES, AND SCORCHING OF THE ENGINE COWLING. NO FIRE WAS EVIDENT, JUST EXHAUST HEAT DAMAGE.