The Monroe County Sheriff’s Office is investigating an accident on Interstate 90-94 near Oakdale Tuesday which left a Wisconsin State Patrol trooper injured.  The trooper was trying to stop traffic on the eastbound interstate due to an accident further down the road.  The trooper’s squad car was hit by an out-of-control semi, then a second one also slammed into his unit.  The trooper’s name hasn’t been released.  He was taken to a nearby hospital with injuries not thought to be life-threatening.