ON MY WEEKLY RETURN RUN ON 7/18 I NOTICED SOME ROCK HAD FALLEN ALONG RIB IN #6 ROOM. WENT BACK ON 7/19 TO TIMBER AREA AND DISCOVERED ROOF FALL.THIS AREA WAS A KNOWN BAD ROOF AREA WITH 4' & 6' FULLY GROUTED BOLTS AND 8 X 8 & 9 X 9 PLATES ON 3' CENTERS. LENGTH OF FALL WAS 100' IN #6 ROOM XCUT #6 ROOM TO #5 ROOM, 55' #5 ROOM, 90' LONG, 6TO 12' HIGH AND 17' TO 20' WIDE.