AN UNINTENTIONAL ROOF FALL WAS DISCOVERED WHILE TRAVELING THE #2 NEUTRAL AIR WAY. THE FALL MEASURED 200 FT LONG X 20 FT WIDE X 4 FT HIGH. ALL ENTRANCES HAVE BEEN BREAKERED OFF. THE LOCATION IS AT SURVEY STATION 283 IN ADJACENT ENTRY 9700 FTFROM ACTIVE SECTION.