Tranz Metro is warning travellers on the Wairarapa-Wellington line to make alternative arrangements Tuesday morning.
It says all services have been suspended because a freight train derailed just south of Masterton when it hit a cow on the track.
There are limited bus replacements available between Masterton and Upper Hutt.
Tranz Metro can't say when the line will be reopened, but says it's hoping for a quick resolution.
