JACKSON, Miss. (AP) — Mississippi prison officials are investigating what they say are five unrelated inmate deaths.

The Mississippi Department of Corrections said Monday that three inmates have died since Thursday at South Mississippi Correctional Institution in Leakesville. Fifty-seven-year-old Albert McGee died Thursday while serving a life sentence for a murder in Jackson County. Thirty-six-year-old Willie Hollinghead died Saturday. He was serving 10 years for selling cocaine in Wayne County. Seventy-year-old Jack Glisson was serving a life sentence for a murder in Jones County and died Sunday.

Thirty-eight-year-old Robert Joseph died Sunday at Central Mississippi Correctional Facility in Pearl while serving a three-year sentence for drug possession in Harrison County. Sixty-six-year-old Charles McCullough died Saturday at Mississippi State Penitentiary in Parchman. He was convicted on charges in Pike and Amite counties.