The CTA Red Line was rerouted for an hour to elevated tracks Monday between the Fullerton and Cermak-Chinatown stations due to a person on the tracks near the Grand station.
The transit authority first announced that trains were standing near Grand about 4:05 p.m., and rerouted service to the elevated tracks around the Loop about 20 minutes later.
Authorities searched for a person walking on the tracks but were unable to fine them, according to a Chicago fire spokesman.
At 5:17 p.m. the CTA announced that trains were resuming their normal service and passengers should allow extra travel time.
Red Line trains were already bypassing the 69th Street station Monday afternoon after a shooting on the South Side platform.