WHILE BACKFILLING 2535 SAD STOPE, A MINER HEARING ROCK FALL, THE SUPERVISOR RESPONDED AND SAW AND HEARD A FALL OF GROUND, THE EXTENT TO WHICH HE DID NOT INVESTIGATE. HE BARRICADED THE ENTRAN CE AND ON 10-22-01 WE INVESTIGATED AND OBSERVED A FALL OF GROUND AT OR ABOVE THE ANCHORAGE OF 7 FT SPLIT SETS IN THE BACK. ESTIMATED ABOUT 500 TONS, ABOUT 50 TONS FELL IN AN AREA BY PERSONNEL.