Hancock County Sheriff Scott Bentzinger says a preliminary autopsy on William Clark, 63 of Sutter, Il. shows that he died of natural causes.
Bentzinger says jail staff started CPR on Clark after noticing he was having difficulty breathing in the early morning hourse of Saturday, Nov. 2.
Clark was pronounced dead at Carthage Memorial Hospital.
Bentzinger says an investigation by Hancock County Coroner Kendall Beals did not reveal any type of foul play or trauma.
Clark was serving a jail sentence for Domestic Battery at the time of his death.