The death of a man whose body was found inside a coal train at Brisbane's port is being treated as suspicious but police aren't investigating it as a murder.

The man's body was found when a carriage containing about 50 tonnes of coal was being unloaded at the Port of Brisbane on Wednesday afternoon.

"There's nothing at this stage to suggest that anything untoward has happened other than somehow this gentleman has made his way into this coal wagon," Detective Inspector Owen Elloy said.

"If anyone did anything I'd say they'd probably be in there as well."

Nothing was found with the body, police are not looking for suspects and the homicide squad isn't presently involved, he told reporters at the scene.

It is understood the death is being investigated as misadventure.

The train the man's body was found on had travelled 11 hours from the Cameby Downs mine near Chinchilla, which is about 300km northwest of Brisbane.

A post-mortem is expected to be conducted in the coming days and a report will be prepared for the coroner.