The North Carolina Department of Correction said that 40-year-old Charles Branch died Monday.
Department spokesperson Keith Acree said in a news release that Branch was found unresponsive in his cell at the Maury Correctional Institution south of Greenville, and he was taken to Pitt County Memorial Hospital where he was pronounced dead at 6:27 a.m.
The SBI said it was requested to investigate the death at the request of the Greene County Sheriff's Office.
Branch was serving 8-to-11 years for convictions in Johnston County as a habitual felon and assault with a deadly weapon on government officers. Prison officials did not have the cause of death and said an autopsy was planned.