By Kate Gregan of RNZ.
KiwiRail says there have been 67 recorded incidents of trains colliding with animals in the past 12 months.
The company confirmed one of its locomotives collided with a herd of cows on the tracks between Ōtorohanga and Hangatiki at the weekend.
KiwiRail said it understood that about 30 cows died, however, RNZ has been told it could be as many as 60.
The freight train travelling from Palmerston North to Hamilton struck the animals wandering in the rail corridor at around 9.30am on Saturday morning.