What was found
AT 80-90 KNOTS, RECEIVED A NR 1 ENGINE FIRE ALERT, AFTER STOPPING AIRCRAFT COMPLIED WITH QRH PROCEDURE, INCLUDING DISCHARGING SINGLE FIRE BOTTLE. FOUND HIGH RESISTANCE TO GROUND 2 MEGA OHMS ON B LOOP CAUSED BY WATER AND CARBON. CLEANED ON ALL CONNECTORS CHECKED FOR DUCT LEAKS, NONE FOUND. TROUBLESHOT THE FIRE DETECTION SYSTEM IAW FIM 26-11-4, NO ADDITIONAL FAULTS FOUND. OK FOR SERVICE. COMPLETED ALL ACTIONS. ACFT OK FOR SERVICE.