A fall of roof occured in 4-d iac h3 & 20 (5-d longwall tailgate) the fall blocked travel out of an alternate route off the longwall. The fall was approx. 16-20 ft high, 100 ft long and 15-16 ft wide. the roof had a visible clay veing and was supported by straps with 8 ft double lock bolts, and lincoln lock cribs drun center of entry.