A semi jackknifed on the outbound lanes north of 1st Avenue on I-55 around 7:30 a.m, according to Illinois State Police.
As of 9 a.m. all lanes were blocked and traffic was backed up to Central Avenue in Summit.
All traffic was being diverted off onto Harlem Avenue.
No other vehicles were involved in the crash.
ISP said no injuries were reported.
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This is a developing story. Check back for updates.