About 3:10 a.m., the man was standing on the platform of the Cicero Avenue stop in the 700 block of North Cicero Avenue, when he stumbled and fell onto the northbound tracks and was struck by a train, Chicago police said.
Chicago fire officials remain on scene and are attempting to extract the man from beneath the train, police said. He is believed to be in critical condition.
Blue Line service has been temporarily suspended between Pulaski and Forest Park, according to the Chicago Transit Authority. Shuttle buses are available.