The Australian Rail Track Corporation, which manages the line, completed the repairs needed to reopen the line at 9am on Monday.

Fire had damaged track infrastructure between Grafton and Casino last Monday, forcing NSW TrainLink to replace all passenger train services north of Grafton with buses.

"ARTC staff and contractors were engaged from right across the country to ensure the network was back up and running as soon as possible," ARTC group executive Peter Winder said.

"It was a an enormous effort from the 71 workers who put in a total of 3850 hours contributing to the safe return of the network."

Mr Winder said it was "incredible" to have the work completed in such a short amount of time.

"The materials to complete the temporary repairs came from all over Australia including Melbourne, Sydney and Grafton," he said.

"The materials were ordered on Wednesday and started arriving on site Thursday morning which is an incredible effort considering the distance travelled."

Further repairs will be required along parts of the damaged line in the next few weeks.

"Trains are currently running at reduced speeds through the Rappville area," Mr Winder said.

"While ARTC's focus was to re-open the track safely, there will be further works required in coming days and weeks to ensure a return to normal operations."

NSW TrainLink is yet to confirm when normal North Coast passenger train services will resume.

The XPT fleet used on the route is already depleted after "cracks" were found in a key locomotive component.