AN UNINTENTIONAL ROOF FALL MEASURING 20'X50'X4' OCCURRED IN AN INTERSECTION IN THE NO. 2 RETURN AIRCOURSE OF 1 SOUTHWEST MAINS BREAK 8 ONE CROSSCUT OUTBY SPAD 2698. NO INJURIES, NO DISRUPTION OF VENTILATION OR DAMAGE TO EQUIPMENT RESULTED FROM THE FALL. THIS AREA WAS NOT TRAVELLED BY THE WEEKLY EXAMINER.