An unplanned Roof Fall was found in the Intake Air Course of 3rd North, Intersection of Entry #9 & XC #7. It is approximately 20' wide by 20' long and 7' high. No one was injured or entrapped. Ventilation was interrupted. Preliminary diagnoses; Strata failure due to water saturating the upper mudstone band, causing it to swell and weakening the Roof Control.