Police say the theft of copper cable and bells from a Hawke's Bay railway bridge and level crossings could lead to a fatal accident.
More than 750m of cable was stolen from a railway bridge north of Clive last month.
Four bells were also stolen from level crossings between April 12 and May 12.
Senior Constable Pehi Potaka said tampering with the rail systems was a huge safety risk to the public and offenders alike.
"Railway core cables are responsible for transmitting power and signals to trains, which is crucial to keeping the rail systems operating safely and efficiently.
"Crossing bells are an essential part of public safety and play a huge role in warning people that a train is approaching. The removal of these bells has the potential to cause fatal accidents."
Potaka said police would take a hard line with any scrap metal yards found to have been receiving the stolen materials.
He urged anyone seeing suspicious activity or damage to rail crossings or bridges to get in touch.
