The Australian Rail Track Corporation (ARTC) has confirmed a a locomotive derailed last night south of Willow Tree.
Last night, just before 8pm, a north-bound bank engine derailed between Ardglen and Kankool.
Emergency services and ARTC infrastructure team personnel attended the derailment site.
The site has been quarantined ready for safety investigators to attend the site this morning.
All rail traffic has ceased in the section between Ardglen to Kankool in any direction until further notice.
NSW TrainLink has advised the 8:05am Moree to Sydney and the 8:40am Armidale to Sydney XPLORER services have been delayed.
Buses will replaced the trains between Moree and Muswellbrook and Armidale and Muswellbrook. At Muswellbrook, customers will join the train for the remainder of their journey.