WARREN (AP) — Maine prisons officials say the death of an inmate this week is not considered suspicious.

Authorities said 68-year-old Paul Henry Gray was being treated for a long-term medical condition when he died Wednesday at a Portland hospital. The exact nature of the condition was not disclosed.

The Houlton man was an inmate at the Maine State Prison in Warren.

He had served 21 years of a 55-year sentence for murder after being convicted of strangling a woman he lived with in 1993.

Per protocol, the death will be investigated although it appears to be of natural causes.