CHESTER, Ill. (AP) — A prison spokeswoman says a guard at the Menard Correctional Center has been assaulted and the facility is on lockdown.

Illinois Department of Corrections spokeswoman Stacey Solano says the unidentified guard was assaulted Tuesday morning in the Chester prison's chapel. Two other staffers who tried to help him also were assaulted. Solano says all injured staffers have been treated for injuries at a hospital and released. Further information wasn't immediately available.

Chester is on the Mississippi River in southern Illinois about 60 miles south of St. Louis.