(Hillsboro)--The Montgomery County Sheriff's Office, State Police, and Montgomery County Coroner's Office is investigating the death of a detainee found Sunday morning.

According to the Sheriff's Office, deputies found the body of 46 year old John Zupsich of Springfield unresponsive in the Montgomery County Jail. Zupsich was pronounced dead at the scene by Montgomery County Coroner Rick Broaddus.

Illinois State Police and Crime Scene investigation were called in to assist with the investigation. Preliminary autopsy results indicated that Zupsich died from natural causes.