Wollongong Police Transport Command officers spoke with the man travelling on a train between Port Kembla and Wollongong about 4pm on Thursday.

They asked to see a valid rail pass which he allegedly did not have.

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Following further inquiries, police discovered the man was wanted for allegedly breaching his bail.

Wollongong District Police Inspector Mark Walker said the man was detained and removed from the train.

"Prior to being taken back to the police station, the man's property was searched which is standard protocol," he said.

"In the man's bag a small amount of the drug ice was found and a small box that had writing on it indicated [the contents] was explosive."

There was also a fuse protruding in the bag.

"Officers took the bag to the car park on the western side and an exclusion zone was created," Insp Walker said.

Police Rescue Squad attended to examine the container.

A number of railway detonators were found and the device was rendered inoperable.

A railway detonator is a coin-sized device that is commonly used as a loud warning signal to train drivers. When the wheel of the train passes over, it explodes emitting a loud bang.

Police seized and removed the device and methylamphetamine.

The man was taken to Wollongong Police Station where he was charged with possessing an explosive in a public place, possessing a prohibited drug, breaching bail and travelling without a valid ticket.

Further investigations were conducted in consultation with the Counter Terrorism Command and police concluded that this is not being treated as a terrorism related offence.

Police remind the public not to misuse or tamper with railway detonators and it is an offence to be in possession of railway detonators.

They may cause serious injury to the person holding them or others.