A ROCK FALL WAS DISCOVERED IN THE #2 ENTRY APPROXIMATELY 70 FEET OUTBY SPAD #533 DURING THE PRESHIFT EXAMINATION AT 8:30 PM. THE FALL WAS APPROX. 20' LONG X 18' WIDE AND 10 FEET IN THICKNESS. THE ESCAPEWAY WAS REROUTED, THE ROCK FALL CLEANED UP AND THE ROOF RESUPPORTED WITH ARCHES. IT DID NOT AFFECT PERSONS, VENTILATION NOR EQUIPMENT.