A ROOF FALL OCCURRED ON THE 3-NORTH SECITON IN THE 10 ENTRY INBY 200-64 AMD CONTINUED INBY FOR APPROX. 70 FT THERE WAS NO INJURIED, ENTRAPMENT OR PROPERTY LOSS. THE FALL WAS ABOVE THE ANCHORAG E AND DID NOT AFFECT VENTILATION. THE FALL WAS 15' WIDE BY 10' HIGH BY 70 FT LONG.