POLK COUNTY, Fla. (WFLA) – Detectives are trying to figure out how a Polk County Jail inmate died on Saturday.

Michael Neupert, 55, was found unresponsive his cell early Saturday morning, the Polk County Sheriff’s Office said.

Jail staff and emergency crews tried to administer CPR, but Neupert could not be revived.

He was taken to Bartow Regional Medical Center, but he did not regain consciousness and was declared dead at 3:24 a.m.

Neupert had been in jail for failure to register as a sex offender. The jail’s medical staff was aware of his history of medical issues, including diabetes, hypertension, COPD, and a recent cerebral vascular Ischemia (insufficient blood flow). Earlier this month, he was admitted to the Lakeland Regional Health Medical Center due to his declining health. He was released 12 days later and transported back to jail and housed in an infirmary. Detectives said a nurse had checked on him ten minutes before he was found unresponsive.

Law enforcement officials have opened four separate mandated, independent investigations into Neupert’s death, which is standard PCSO policy for when an inmate dies.

An autopsy to determine his cause of death was tentatively scheduled for Monday, August 28.

Neupert had served multiple stints in the Florida Department of Corrections prison and the Polk County Jail. His previous charges include 31 counts of possession of child pornography, violation of probation, failure to register as a sex offender, and driving while license suspended or revoked.

No further details regarding his death are available at this time.STORIES OTHERS ARE CLICKING ON-