EMPLOYEE WAS OPERATING A KOMATSU WHEEL LOADER WHEN CAB BEGAN TO FILL WITH SMOKE. EE DISMOUNTED AND NOTICED A FIRE HAD STARTED IN BACK OF LOADER.HE IMMEDIATELY CALLED THE FIRE DEPARTMENT, WHICH RESPONDED AND PUT OUT THE FIRE. NO ONE WAS INJURED AND NO PROPERTY DAMAGE, OTHER THAN TO LOADER. CAUSE APPEARS TO BE ELECTRICAL IN NATURE.