CHICAGO (CBS) — Police were investigating Saturday after a man was found dead on a CTA bus downtown.

The 46-year-old man was found slumped over in a seat on the Chicago Transit Authority bus at 9:37 p.m. Friday, police said.

The bus was on Congress Plaza Drive, a crescent-shaped street in Grant Park that runs just east of Michigan Avenue at Ida B. Wells Drive.

The man was rushed to Northwestern Memorial Hospital, where he was pronounced dead, police said.

No signs of trauma were visible on the man’s body, police said.

Area Central detectives were investigating Saturday afternoon.