Trains between Wairarapa - Wellington are expected to resume by 10.25am, after a train ploughed into a herd of cattle.
The freight train was travelling south of Masterton at about 5.30am on Wednesday when the mob was hit.
Tranz Metro says the number of dead and injured cattle are still unknown.
Morning commuters were put on buses to get them to the Wellington, but regular service is expected to resume by 10.25am.
Tranz Metro says there is no indication of how the cattle got there. Efforts will now be made to find their owner.