A remote-control locomotive was "hijacked" from a Hamilton railyard but failed to get very far before shutting down.
KiwiRail has launched an internal investigation into last Friday morning's incident in which the locomotive left its Te Rapa base and headed towards Frankton.
The low-speed locomotives, which are used to assemble wagons, do not have a driver on board and are controlled remotely by someone walking alongside them with a radio control. They can only travel up to one kilometre before they lose radio frequency and automatically shut down.
A KiwiRail spokeswoman said the incident did not involve a security breach.
However, she would not be drawn on exactly how the security-fenced yard was entered, whether staff had been reprimanded or how the locomotive was able to travel so far after-hours.
She says there was no danger to staff or the public.
NZN