A liquid nitrogen leak from a large gas cylinder on a train at Pukekohe Railway Station has stopped services in the area.
The Fire Service was called to the leak just after 10.15pm.
All trains in the area have stopped while firefighters clean up the leak and make the area safe, a Fire Service spokesman said.
Police are assisting the Fire Service at the scene, a Police spokeswoman said.
Liquid nitrogen is a colourless clear liquid which is used in a variety of ways including as a coolant for computers and in medicines to remove warts.