An unintentional roof fall occurred in 3 North Mains in #2 entry from 11 1/2 wall to inby 10 1/2 wall. The fall measured approximately 12-15' high by 16' wide and 300' long. There were no injuries as a result of this incident. The event occurred due to humidity in the area and a lateral shift which caused the 8' bolts to fail at there couplers.