Rail services using lines between Canterbury and the West Coast could be out of action for sometime, following a devastating blaze.

A fire ripped through 300-hectares of conservation land between Staircase and Craigieburn in Canterbury - damaging the railway line.

The fire has covered an area involving eight rail bridges, a number of which have been damaged.

KiwiRail Group general Manager of Network Services Todd Moyle said they will get in and assess the bridges tomorrow, and have an estimated operational time by the end of the week.

He said the crews will find a way to get it functioning again.

"I have full confidence in our teams and their ability to get in there and come up with innovative solutions to get these lines back and operational."

Moyle said it's still too soon to know how quick or costly the repairs will be.

"It will take us a day or two to really get an understanding of the full extent of that damage and be able to make an estimate on the time to repair it."