(Clinton County, IL)  —  Clinton County authorities are conducting an investigation after a man was found dead in a pickup that had been submerged in Sugar Creek.  A witness told KSDK-TV that he saw the vehicle drive into the water early Tuesday morning and it was quickly washed away.  Rescue teams found the truck under water and jammed up against a levy.  The driver was drowned and found in the cab of the truck when it was pulled from the water.  Police believe the victim was the only one in the truck.