Chicago police are investigating after an elderly man was found dead on a CTA train early Saturday in the Loop. The man, whose exact age was not known, was seated on a Blue Line train when passengers realized he was unresponsive around 1 a.m. in the 300 block of South Dearborn Street, Chicago police said. The man was pronounced dead at the scene, police said. His name hasn't been released. The cause of death was unknown pending an autopsy from the Cook County medical examiner's office.