A man who was incarcerated at the Maine State Prison in Warren died early Thursday morning, but the Maine Department of Corrections said his death was not related to COVID-19.

Matthew Fleury, 51, was serving a 17-year sentence for gross sexual assault. He was sentenced in 2007, and his earliest release date was in 2022. The department did not say what caused Fleury’s death.

The department said his death at 12:55 a.m. Thursday was attended by medical personnel, and the Maine State Police and the state medical examiner were notified as required by department policy.