A fire burning on the tracks of the Christchurch to Greymouth rail line has brought the TranzAlpine and some freight services to a halt.
The track between Cass and Springfield has been closed because of the blaze, but it poses no risk to trains or staff.
KiwiRail group general manager network services Todd Moyle said staff will assess the damage once the fire is under control and the site is safe to access.
"Only when that has been done will we be able to comment on when the track will be open again."
Bridges and signals equipment had been damaged, Moyle said.