ROOF FALL OCCURRED AT 11N-O BLOCK. NO PERSONS OR EQUIPMENT INVOLVED, TWO HVAC CABLES WERE TORN DOWN. FALL DIMENSIONS WERE APPROX 50' X 35' X 0-11' THICK. INITIAL AND SUPPLEMENTAL BOLTS INSTALLED WERE 8' RESIN. THE FALLEN MATERIAL WILL BE REMOVED AND THE AREA SCALED AND REBOLTED.(AREA INVOLVED WAS ADJACENT TO AN AREA THAT HAD PREVIOUSLY FELL AND BAD MATERIAL BLASTED DOWN