A roof fall occurred at the intersection of E. Corridor #1 entry and C-Mains #2 entry at 60 x-cut of E. Corridor. The fall was approx. 10'-12' high across the intersection. There were no injuries. The area was dangered off and posts were set on all 4 sides of the intersection. Ventilation was not effected. The alt escapeway for the C district was re-routed around the fall area.