THE safety regulator is investigating after a passenger train went through a stop signal enroute to Gunnedah.
The NSW TrainLink service passed the stop signal at an estimated speed of 90km per hour on June 10, entering into the Gunnedah Coal siding.
Investigators are probing the circumstances surrounding the "signal passed at danger" incident, which occurred at 4.45pm and saw the train proceed into the siding by 300m.
The NP43 train service was carrying passengers from Sydney's Central Station through to Moree, and had just left Werris Creek before the incident occurred.
No one was injured in the incident.
The New South Wales Office of Transport Safety Investigations (OTSI) is leading the official probe on behalf of the Australian Transport and Safety Bureau (ATSB).
As part of the preliminary investigation, the ATSB has been told the train driver reported the sun was "directly behind the signal and he could not see the stop indication".
"The train stopped approximately 200m before reaching the Gunnedah Coal loop departure points," the ATSB said.
"The driver was sent for post incident drug and alcohol testing and tested negative."
The ATSB said as part of its investigation, officers "will obtain information from the train data logger, track circuitry data and interview relevant persons".
The safety regulator will then release a report into its investigation, which is expected to be completed by the end of the year.