The Benton County Sheriff's Office is investigating the death of an inmate.

 Sheriff Shawn Holloway says jail staff found 53-year-old Timothy Plank unresponsive in his cell around 2:00 p.m. Friday afternoon. Plank was taken to Northwest Medical Center where he was pronounced dead. An investigation is underway by Benton County Sheriff’s Officer Internal Affairs Division and the Criminal Investigation Division.

 Plank was in jail on charges of aggravated robbery, four charges of aggravated assault, aggravated assault on a correctional facility employee, possession of a controlled substance, theft of property, and obtaining drugs by fraud.