CFD said in a post on X just before 7:45 a.m. that the fire in the 200-block of South Wabash Avenue was put out with fire extinguishers.
No one was injured in the incident, but the train was evacuated, CFD said.
The fire involved one car of the train, according to fire officials.
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The CTA said in an post on X that Loop trains were standing at Adams/Wabash due to the incident.
A spokesperson said just before 9 a.m. that trains were operating normally again, after experiencing delays due to smoking brakes on a Brown Line train at the Adams/Wabash station.
Chopper 7 was over the scene, and some smoke was visible about 7:45 a.m., as Chicago firefighters and CTA workers walked along the tracks in the area.