The former Boston Legal star was believed not to have been wearing a seatbelt when his Jeep came off the road near Madison, WI and rolled down an embankment, smashing into two trees on Monday morning.
According to MTV News, Mentell was thrown from the car and later died at the scene.
Chief deputy John Pepper told reporters: "It looks like [Mentell] had been there for several hours. There are a lot of trees in that area, so if you were driving on 39, you wouldn't be able to see the vehicle. The farmer was traveling on Moscow Road after the sun came up, and he saw the Jeep in a field."
Pepper went on to say that there had been "no indication" that alcohol or drugs had played a part in the crash, although routine toxicology reports will not be ready for six to eight weeks.
The actor and musician was best known for his role as Garrett Wells in ABC's hit legal drama from 2005 to 2006. He was also cast in several feature films, including last year's Disney movie G-Force.
