The finding is the result of an autopsy on 21-year-old Thomas Sarwark. Coroner Beth Kimmerling said his preliminary cause of death is multiple blunt force injuries.
Forensic toxicology tests have been ordered.
Sarwark was an Illinois State University freshman and veteran of the U.S. Army who died early Friday morning.
For an unknown reason, authorities said he drove his pick-up truck the wrong way on southbound I-55 near mile marker 145 and collided with a semi-tractor trailer, which caught fire.
Sarwark, from Burr Ridge, Illinois, was pronounced dead on scene. Two people from the semi were taken to the hospital.