An investigation is underway in Morgan County after an inmate was found unresponsive in his cell Saturday afternoon, according to the Tennessee Bureau of Investigation.

The agency said jail staff found Jamie Jones, 45, unresponsive in his cell and performed CPR while waiting for an ambulance to arrive but could not revive him.

An autopsy will be performed to determine his exact cause of death, according to the TBI.

Russell Johnson, 9th District Attorney General, said the cause of death will likely be medically-related to illness.

"According to my verbal report from TBI, there was no sign of trauma and there was no altercation before or during his death involving other inmate(s) and/or corrections officer(s). It was not a suicide," Johnson said.

According to Johnson, Jones had been in an isolation cell several days "de-toxing" and was receiving medical treatment from the Morgan County Sheriff's Office nurse.

Hours before, another inmate had been placed in the same cell with him and he was the one that alerted corrections officers and that Jones was shaking as if having some sort of medical episode or problem, Johnson said.

Toxicology reports could take three to four months.