BELLEVILLE – State officials have a plan to stabilize a mine that collapsed under a school in southwestern Illinois. The ground beneath the Wolf Branch Middle School in Swansea dropped almost 25 inches when the abandoned Summit Mine collapsed in September, according to the Illinois Department of Natural Resources. The agency said the collapse caused “extensive structural damage” to the building. The department announced Wednesday that it will pump a concrete mixture into the mine to halt gradual sinking, The Belleville News-Democrat reported.