Twenty-thousand people booked to take the Tranzalpine train across the Southern Alps in the next few weeks will have to go by bus after fire damaged bridges on the route.
A blaze near the Broken River viaduct in the foothills west of Springfield tore through about 300 hectares at the weekend.
Fire damage to tracks, bridges and signal systems has put the Christchurch to Greymouth railway line out of action for at least six weeks.
The Cass to Springfield section of the railroad is closed, affecting the TranzAlpine passenger service and freight services carrying coal and dairy products from the West Coast.
One bridge was damaged extensively and 12 wooden piles would need to be replaced.
Kiwirail spokeperson, Todd Moyle, said the company was disappointed about what happened.
"We have to get back in there and fix them, in a pretty remote location as well, so it is extremely difficult to get in there and make those repairs."
The company was still assessing the full extent of the damage and an investigation was currently underway to determine the cause of the fire.
The Tranzalpine train is suspended until 3 April.
Full refunds have been offered as well as short-term bus services.