CHICAGO (CBS)– A Calumet Park man was struck and killed by a semi-tractor trailer Monday morning on Interstate 57.

Illinois State Police said the the truck was headed north on I-57 near 103rd Street around 4:55 a.m., when it hit a 25-year-old man who was in the right lane of traffic.

The victim was taken to Advocate Christ Medical Center in Oak Lawn, where he was pronounced dead. Police said it was unclear why he was on the expressway.

Two lanes of I-57 were closed while police investigated, but reopened by 7:40 a.m.