2 Marion County teens were seriously injured after they collided into the rear of slow moving tractor pulling a field planter yesterday morning. Both teens were airlifted from the scene. Steven James Thompson, 17 of Knoxville was flown to the University of Iowa in Iowa City and Derk Levi Springer, 18 of Bussey was taken to Mercy Des Moines by helicopter. The accident remains under investigation. The Mahaska County Sheriff’s Office, the Oskaloosa Police Department and the Oskaloosa Fire and Rescue all responded to the scene.