A roof fall occurred in the C-1 butt section approx 100' from the face of C-1 butt, not being mined. The roof fall was 16' to 18' in width, 25' in length and 4 1/2' in height. Area was bolted with 4' resin bolts. No one was working in area. Mining was being done in return rooms. No ventilation or escapeways were affected.