Police believe a man's body spent 11 hours in a coal wagon travelling from an inland mine before it was found at Brisbane's port some 350 kilometres away.

Detectives investigating the discovery at the Port of Brisbane described the death as "unusual to say the least" but it was being treated as non-suspicious.

A body has been discovered in a coal train at the Port of Brisbane. Credit:Nine News Queensland/Twitter

Detective Inspector Owen Elloy said Queensland Rail workers found the man's body in the doors of a coal wagon about midday on Wednesday, after the train delivered its load of coal from Chinchilla, about four hours north-west of the city.

He added the investigation would go to the coroner, but it was clearly a case of misadventure and there was nothing to suggest anything untoward had happened.