Victoria's police chief says his officers are continually finding items linked to the Metro train network for sale online.
A black market for Metro train keys, passes, pass codes and uniforms has been revealed after vandals started and derailed train at a Victorian depot.
A set of stolen keys was used to start the train at the Hurstbridge holding yard on Melbourne's outskirts in the early hours of Wednesday.
But the train didn't get very far before security equipment derailed it and any plans for a joyride.
Victoria's Police Chief Commissioner Graham Ashton says police are continually finding items linked to the train network online.
"We've got a number of investigations looking into it, particularly on stolen keys," he told 774 ABC radio on Thursday.
"We continually find them available on line, people seem to be buying them online."
He said police charged some people in relation to the sale and purchase of those items in recent weeks but investigations relating to Wednesday's incident were continuing.
Security has been stepped up across the entire network.