All of KiwiRail's Matangi trains that operate in and around Wellington have been pulled from service.
The Korean manufacturers who made the trains rang KiwiRail today to tell them the trains were in need of immediate inspections.
There are concerns around the part that joins two carriages of the commuter trains together.
TranzMetro spent $235 million buying the 48 trains, with the last one arriving in New Zealand earlier this year.
Buses will replace the trains this evening, running on a half hourly timetable.
