KiwiRail says it is too early to know what caused a locomotive to derail near the mid-Canterbury town of Hinds.
Emergency services were alerted shortly before 8am on Monday that the engine had derailed near Delamaine Street.
A KiwiRail spokesperson says the driver walked away from the accident with no injuries.
The locomotive was on its side next to the tracks and staff were at the scene working to remove the engine.
The locomotive was en route from Christchurch to Dunedin.