The male victim was taken to Stroger Hospital after the incident, CFD said.
The CTA tweeted just before 5:30 a.m. that Blue Line trains were standing at Division due to an unauthorized person on the tracks.
Trains were running again with delays just before 5:45 a.m., the CTA said.
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It was not immediately clear how the person ended up on the tracks.
This is a developing story; check back with ABC7 Chicago for updates.