THE ABOVE HAS EXPERIENCED A NON-INJURY, UNINTENTIONAL ROOF FALL ON BOX CUT MAINS FOR MMU 012-0 INTAKE AIRWAYS APPROXIMATELY 12 CROSS-CUTS INBY THE BOX CUT PORTALS IN #8 ENTRY. THE ROOF FALL WA S 30 FEET LONG , APPROX 6 FEET THICK AND 20 FEETWIDE IN AN INTERSECTION. IT IS UNKNOWN OF THE EXACT DATE OF THE FALL, BUT IT WAS DISCOVERED 4-19-00.