Lengthy repairs will have to be carried out on parts of the line with Transport Minister Andrew Constance revealing some of the damage on Wednesday.

"Some of the aftermath of the devastating bushfires currently burning in Northern NSW," Mr Constance said, alongside a photo of damaged line posted to social media.

"Stretches of the North Coast rail line have crippled by fire, with the Rappville Rail Bridge destroyed.

"Thinking of all those affected by bushfires across the state."

The Australian Rail Track Corporation, which manages the line, has confirmed extensive repairs will be needed but it is yet to conduct a fully assess the damage.

"The highway is currently closed and RFS have advised that the area is too dangerous to enter and it will be at least approximately 48 hours before detailed assessment of the track damage is possible," ARTC group executive Peter Winder told the Newcastle Herald.

"An early inspection with the RFS indicates substantial damage to bridges, track, signalling and level crossing infrastructure.

"The rail line will be impacted until at least early next week and we expect to be able to make further assessments once the rail corridor is safe to finalise track inspections and will be following NSW RFS advice with respect to this.

"ARTC is currently mobilising repair crews and materials."

Transport for NSW is yet to confirm how NSW TrainLink services between Sydney and Grafton, Casino and Brisbane will be impacted. It is has been contacted for comment.

NSW TrainLink is already battling with a reduced fleet, after it was revealed last month there was issues with a key component of XPT locomotives.

The daily Sydney to Grafton XPT service has not ran for weeks and was already expected to be replaced by buses for some months while critical fleet repairs took place.

North Coast XPT services run through the Hunter and usually stop at Fassifern, Broadmeadow, Maitland and Dungog.