A man serving a two-year sentence at the Delta County Jail was found dead in his cell Saturday afternoon.

Delta County Sheriff Fred McKee said initial information indicates that Justin Stieb may have died of natural causes, but he stressed that the investigation into the death has not concluded. There does not appear to be evidence of any criminal conduct, McKee said.

Stieb had received medical care the evening before his death and was in an isolation cell so his health could be monitored, McKee said. He was discovered deceased during a routine check; McKee said that 20 minutes before, Stieb had checked out OK.

The Colorado Bureau of Investigation is looking into the matter, which is standard procedure for in-custody deaths.

An autopsy was being conducted on Monday.