Red Line trains were rereouted to the elevated tracks Tuesday morning after smoke was detected at the Grand station.
Firefighters were called to the station at about 7:20 a.m. for a smell of smoke coming from debris on tracks, CTA spokesman Brian Steele said.
No trains were stopped, but trains heading north and south between Fullerton and Cermak/Chinatown were rerouted to elevated tracks. Power was cut off through the regular route, Steele said.
Trains were going back through the subay shortly before 8 a.m.