ABC7's Roz Varon reported the staging area was at 700 North Milwaukee at approximately 8:25 a.m. Although trains were not passing through earlier Tuesday, they were moving again as of 9 a.m.
Five ambulances were sent as a precautionary measure.
An EMS Plan I and a still-and-box alarm response were called after smoke was reported in the subway.
(The Sun-Times Media Wire contributed to this report.)