Five ambulances were sent to the scene as a precautionary measure. No one was injured.
While crews worked the scene, Red Line trains were rerouted through the elevated tracks.
The smoke was caused by train brakes and there was no fire, according to CTA spokeswoman Catherine Hosinski.
An EMS Plan 1 -- which sends five ambulances to the scene -- and still-and-box alarm were called to the report of a fire about 2 p.m., according to Fire Media Affairs spokesman Quention Curtis.
Hosinski said Red Line trains were rerouted to the elevated tracks between Fullerton and Cermak-Chinatown so power could be shut off in the subway. That lasted for about 12 minutes and service was back to normal as of about 2:30 p.m.
The Sun-Times Media Wire contributed to this report.