A ROOF FALL WAS FOUND IN THE #2 ENTRY OF THE OLD 1 WEST MAINS AIRCOURSE OUTBY MP 2 STATION. THE FALL IS APPROXIMATELY 25' LONG BY 25' WIDE AND 8' HIGH. AREA WAS REBOLTED WITH 8' INSTALL II RE SIN ASSISTED ROOF BOLTS WITH SCREENS & HEADERS. FALL CAUSED BY BROKEN ROOF ABOVE THE BOLT ANCHORAGE. VENTILATION NOT AFFECTED BY IT DID AFFECT PRIMARY ESCAPEWAYS. WORK STARTED TO SUPPORT FALL.