THE LAST ROUND HAD BEEN SHOT IN A CUT AND FILL SECTION. THERE WAS A WEDGE SHAPED SECTION OF THE BACK THAT WAS NOT FULLY SUPPORTED BY BACKFILL ONTHE LEFT RIB. WHEN MINERS CAME IN THE SECTION ABOVE THE ROUND THAT HAD BEEN SHOT, AND THE ROUND BEFORE THAT HAD BEEN SHOT, THERE WAS GROUND FAILURE.