A bridge on the Christchurch-Greymouth line between Cass and Springfield has been extensively damaged by a scrub fire that's still burning, says KiwiRail.
The 300 hectare scrub and alpine vegetation fire broke out in foothills inland from Springfield yesterday.
Fire service crews supported by helicopters are continuing to fight flare-ups before winds pick up this evening as forecast.
The Department of Conservation's North Canterbury manager Kingsley Timpson said while the fire was under control, hotspots continued to flare up and fire crews had been kept busy trying to contain them.
He said there was the potential for the fire to spread as strong winds and high temperatures were forecast for tomorrow.
KiwiRail's network manager, Todd Moyle, said a full assessment of the damage would be carried out when it was safe for staff to access the site.
He said early indications were that one bridge had been badly damaged, and there was damage to other bridges and viaducts in the area.
The Cass to Springfield section of the Christchurch to Greymouth railroad is closed, affecting the TranzAlpine passenger service and freight services carrying coal and dairy products from the West Coast.