A roof fall occurred above overcast at Main South Belt line at XC 27. The fall occurred when roof bolts pulled out of the strata in the roof. The material was 6"" thick x 10' long x 15'wide in size on top of the crushed overcast. Damage to the overcast disrupted main ventilation in the area. MS belt line was damaged for approx. 15' and no miner was injured in the event.