A ROOF FALL OCCURRED IN THE #4 ENTRY AT #0 BK OF THE 21 BUTT SECTION. THIS IS THE RETURN AIRWAY OFF 21 BUTT SECTION. FALL WAS IN INTERSECTION ADN WAS 6'H X 30'L X 17'W. NO EQUIPMENT INVOLVED A ND IN INJURIES. AREA WAS SUPPORTED WITH 6' HI TECH BOLTS, DWYDAG SLINGS, ON 4FT CENTERS.