The footwall slip that intersected with the hanging wall contributed to ground failure at 41W 8400 A5. The area was posted and barricaded at 11:30 PM pending further investigation. At 12:40 AM the failure had propagated to approximately 50' wide x 40' along strike x 20' high. The 50' cable bolts installed on 6' centers remained in place. MSHA was notified by telephone.