AN UNINTENTIONAL ROOF FALL OCCURRED ON THE TILLEY MAINS 1 BRK INBY SPAD #3142. APPROX. 1300FT. FROM THE ACTIVE FACE, IN THE RETURN ENTRY. VENTILATION WAS NOT AFFECTED. ALL ENTRANCES HAVE BEEN BREAKERED OFF TO THE FALL. THE FALL MEASURED 20'L X 20'W & 6'H. THE FALL WILL NOT BE REHAB-ILITATED.