The shooting took place on a train at the CTA Halsted station around 12:22 p.m.
Two men were fighting when a 44-year-old man was shot in the foot, Chicago police said.
The man was taken to the hospital with non-life threatening injuries.
The Orange Line service was halted for about one hour between Adams/Wabash and Ashland.
It was also suspended to Midway airport, the CTA said on X.
Service fully resumed around 1:30 p.m., with delays, the CTA said.
No other information was available.
No one is in custody. CPD Area One detectives are investigating.
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