KiwiRail anticipates the only rail link between Canterbury and the West Coast could be out for at least six weeks following fire damage at the weekend.
The fire has damaged bridges, track and signal systems and affected services including the renowned TranzAlpine journey, plus coal and dairy freight services.
The large blaze broke out on conservation land between Cass and Springfield in the early hours of Saturday morning, near the rail bridge over Broken River.
About 300ha of scrub was destroyed. The cause of the fire is still unknown.
KiwiRail group general manager of network services Todd Moyle said crews from around the country would be brought in to tackle the line reinstatement as soon as possible.
"Hot and windy conditions at the weekend meant several of our bridges along the route were damaged, including one bridge where 12 wooden piles will need to be replaced.
"We are still working through the quickest course of action to reinstate the line. Heat spots in the area remain a concern.
"We are very disappointed for the many international tourists who have travelled to New Zealand and will now miss out on the opportunity to enjoy our world-renowned TranzAlpine service. Full refunds are being offered as well as short-term bus services."
Mr Moyle said KiwiRail was working closely with its freight customers on the fast reinstatement of train services.
The closure means two of the South Island's major rail lines are now out of action.
The Christchurch to Picton line sustained major damage during the Kaikoura earthquake in November.
There are three main users of the Christchurch-Greymouth line. KiwiRail's TranzAlpine passenger train makes the trip from Christchurch to Greymouth and back daily.
Westland Milk Products (WMP) transports milk to and from its factory in Hokitika, and Solid Energy rails Stockton coal to Lyttelton for export.
WMP supply chain manager Raul Elias-Drago said WMP had "good systems" in place to manage disruptions to its transport network.
"There is no serious impact on our internal and external goods movements as we have the road transport capacity to ensure business continuity," he said.
Solid Energy did not respond in time for the Westport News deadline today.
'Vital' tourism link
Grey District Mayor Tony Kokshoorn said if the line continued to stay closed, tourism in Greymouth and the wider West Coast would be significantly impacted.
"It's a real worry for us, because the TranzAlpine ferries in a huge amount of people here to the West Coast? It's a vital link."
Although for many tourists Greymouth was just the place to pick up a rental car, they were still spending money in the town, he said. The fact they then journeyed to other parts of the Coast made the railway's closure a Coast-wide problem.
"It will have an impact there's no doubt about it."
In summer, the train was six carriages long. In the mid-winter it got down to about three, he said.
Luckily the West Coast was experiencing one of its better tourist booms, which should be able to absorb some of the loss, Mr Kokshoorn said.
- Westport News