WARREN, Maine — The death Friday afternoon of a Maine State Prison inmate is suspicious, said Maine Public Safety spokesman Stephen McCausland on Saturday.

An autopsy is planned for Saturday afternoon by the Maine Medical Examiner’s Office.

The Maine attorney general’s office and state police are investigating the death of Micah Boland. Boland, 37, had served about six years of a 22-year sentence for gross sexual assault.

The manner of the death is not being released.

Boland died at approximately 4:40 p.m., the state reported.

Boland was sentenced in 2008 in Waldo County Superior Court by Justice Jeffrey Hjelm to 22 years for sexually assaulting a 4-year-old girl in Liberty in March 2007. The girl’s family had left her with Boland for a short time, according to testimony at the jury-waived trial.

According to Deputy District Attorney Eric Walker, the sentencing of Boland was the first use of Jessica’s Law in Maine, in which penalties are increased based on the young age of the victim.

In the past five years, three prisoners in Warren have been beaten to death. In one case, a prisoner was acquitted in connection to the death, and in the second, the defendant pleaded to the lesser offense of aggravated assault. The third case is set to go to trial in March.