The Arkansas Department of Correction says an inmate has died after being found unresponsive in his cell.

Spokesman Solomon Graves says 54-year-old inmate Dan Shelton was pronounced dead at 2:16 a.m. Thursday at the maximum-security prison in Tucker.

Prison staff discovered Shelton unresponsive at 1:57 a.m. and provided emergency medical treatment before transferring him to the infirmary, where he was pronounced dead.

A suspected cause of death has not been released. Arkansas State Police and the Department of Correction are both investigating the death.

Shelton was serving a 40-year sentence from Jefferson County for kidnapping, burglary and other charges. He is the second inmate to die at the prison in Tucker this week.

Officials say 49-year-old David Mulkey was found unresponsive in his cell Sunday and later pronounced dead.