Blue Line train service in Chicago came to a halt on Tuesday evening while an unauthorized person was on the tracks, prompting "major delays," authorities said. Around 7 p.m., train service on the Blue Line was stopped near the Grand station because of a person was on the tracks, the Chicago Transit Authority said. Crews were still working to restore service as of 8 p.m., according to the CTA website. Video shared with NBC Chicago showed a group of police officers and fire department personnel investigating a grate on the 700 block of North Milwaukee Avenue that appeared to lead down to the underground CTA tracks. The person who took the video said they believed authorities were talking with the person on the tracks through the grate, though that information was not immediately confirmed by authorities #cta #blueline #chicago