The death of a prisoner Thursday at the Maine State Prison in Warren is under investigation by the Maine State Police and the Medical Examiner’s Office.

The inmate was identified in a press release Thursday night by the Department of Corrections as Donald Riley, 67.

Deputy Commissioner Jody Breton said Riley died around 2:15 p.m. Thursday. He had served just over one year on a 9½-year sentence for gross sexual assault. He was also serving a concurrent two-year term for burglary.