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.

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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.

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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.

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Area Central detectives were investigating Saturday afternoon.