Pacific National coal train derails in NSW Upper Hunter

A second Pacific National coal train is being examined after a derailment just weeks after a runaway train incident on the same freight track.

The lead wheel, or bogie, of the locomotive derailed just before midday, shutting the line between the Upper Hunter and Tamworth.

Rail safety investigators will examine the scene.

A coal train locomotive has derailed in the NSW Upper Hunter less than two weeks after a runaway unmanned train operated by the same company reached 90 kilometres per hour.

The Australian Rail Track Corporation (ARTC) confirmed it was notified about an incident just before midday.

ARTC was advised the lead wheel, or bogie, of the Pacific National coal train derailed at Ardglen Loop, a stretch of track between the Upper Hunter and Tamworth.

Pacific National has confirmed the incident.

"The incident occurred on the Ardglen loop and has resulted in disruption to rail traffic through the area," a spokesperson said.

"There have been no reports of injuries to the train crew.

"The train has been secured and our teams are responding to the incident."

ARTC said the site had been "preserved" pending the arrival of investigators from the Office of the National Rail Safety Regulator (ONRSR).

The derailment comes three weeks after an incident involving an unmanned Pacific National train travelling up to 90km/h over 20 kilometres without a driver on board.

An interim report found the three locomotives and 96 wagons reached speeds well over the safe limit on July 25, and only came to a halt after rolling backwards for 5 kilometres.

Last week ONRSR updated its advice about reporting requirements for rail transport operators.

It said "a notifiable occurrence means an accident or incident associated with railway operations that must be reported to ONRSR".