What was found
MECHANICAL INTERRUPTION IN ANCHORAGE AT 1522Z DUE TO LOWER CARGO FIRE WARNING HORN WENT OFF 3 TIMES. OPENED BOTH BELLY DOORS IMMEDIATELY UPON AIRCRAFT RETURN. FOUND NO SMOKE OR FIRE. UNLOADED BELLY'S AND PERFORMED LOWER CARGO SMOKE/FIRE PROTECTOR TEST, IAW HOLLINGSHEAD INTERNATIONAL AIRCRAFT MAINT MANUAL SUPPLEMENT. SYSTEM TESTED OK, NO FAULTS OR DEFECTS FOUND. SUSPECT FREIGHT BEING STACKED TO CEILING WAS THE CAUSE. DEFERRED THE SYSTEM FOR FURTHER TROUBLESHOOTING. FURTHER TESTING, AFTER FLIGHT REVEALED NO FAULT, DEFERRAL REMOVED AND AIRCRAFT CONTINUED IN SERVICE.