The passenger was attacked after asking three males to stop smoking on a Red Line train about 2:30 a.m. Jan. 2 in the 100 block of West 69th Street, Chicago police said.

Chicago police are searching for three suspects who violently robbed a CTA rider who asked them to stop smoking on a train car earlier this month on the South Side.

Chicago Police are seeking help from the public in identifying three men involved in a beating earlier this month on a CTA Red Line train. According to police, a man asked someone to stop smoking on the train.