Authorities say an inmate at the Maine State Prison who died Wednesday was being treated for a long-term medical condition and his death is not considered suspicious.

The Maine Department of Corrections said Wednesday that Paul Henry Gray, 68, died at 5:30 a.m. at Maine Medical Center in Portland.

Gray had been in prison for 21 years, serving a 55-year sentence for murder. The Houlton man was convicted in 1993 of strangling a woman he lived with.

In accordance with department policy, Gray’s death will be reviewed by the Maine State Police and the Office of the State Medical Examiner. State Police spokesman Steve McCausland said there is no indication of foul play and that Gray died of natural causes. He did not elaborate on what medical condition Gray had.

Gray was scheduled to be released in 2028.