MONTICELLO, Wis. -- An Illinois man is seriously injured following a crash in Monticello Sunday night.

The Lafayette County Sheriff's Office reported the crash occurred on County Highway W between the intersections of Dimmicks Road and Blackhawk Road at 6:39 p.m.

An initial investigation showed a 20-year-old Illinois man was operating a 2009 Harley Davidson, traveling eastbound on CTH W when he failed to negotiate a curve. He left the road onto the gravel shoulder on the south side of CTH W and lost control of the motorcycle and overturned. The man was ejected from the vehicle during the crash, and the motorcycle was severely damaged and towed away from the scene.

The man was taken to Lafayette Hospital and Clinics in Darlington, where he was transferred to UW Hospital by Medflight.

The sheriff's office reported speed and alcohol are suspected to be contributing factors and he was not wearing a helmet at the time of the crash.

The crash remains under investigation by the Lafayette County Sheriff's Office.