A ROOF FALL MEASURING 12' BY 6' BY 4' THICK OCCURED ALONG #3 TRACK BELT, 2 BLKS IN BY SPAD #636,THIS IS A NEUTRAL ENTRY AND AIRFLOW WAS NOT IMPAIRED. HOWEVER THE TRAVELWAY IS CLOSED TO RAI L TRAFFIC UNTIL THE FALL CAN BE CLEANED AND SUPPORTED. THE AREA WAS BOLTED WITH 48 IN RESIN. THERE WERE NO INJURIES OR OTHER LOSS.