ROCK COUNTY, Wis. (CBS 58) -- A 59-year-old man is dead after a Rock County crash on Friday, Jan. 10. 

It happened on I-39 SB near Mile Marker 182 near Beloit. 

According to Wisconsin State Patrol, a Rock County plow truck was clearing snow from the shoulder on Interstate 39/90 near Mile Post 182. A semi-tractor was traveling in the left lane and struck the rear passenger side of the plow truck. The impact caused the trailer to jackknife and block all southbound interstate lanes. 

The driver of the semi-tractor trailer, a 59-year-old from Milwaukee, was fatally injured. The plow truck driver was not injured. 

The Wisconsin State Patrol is investigating.