CREW WAS MAKING A BELT MOVE IN 1 SOUTH PINE GULCH SECTION WHEN FOREMAN HEARD ROOF WORKING AT X CUT 8 & 40 IN THE MAIN ENTRY. ROOF FELL APPROX. 20' LONG 20' WIDE IN THE INTERSECTION. AREA HAD A DDITIONAL ROOF BOLTS AND ADDITIONAL TIMBER SET PRIOR TO ROOF FALL REPORTED TO TRINIDAD OFFICE 3:45 9-18-00. AREA WAS TIMBERED OFF.