UPDATED: Gwydir Highway was reopened at 5.15pm, Sunday, December 28.

THE Gwydir Highway east of Collarenebri is still closed in both directions as police and emergency services attend a tragic, single vehicle accident.

The accident, involving a Toyota Landcruiser, near the Cryon Road turn-off, about five kilometres east of Collarenebri, occurred at around 10pm last night.

One man was killed in the accident and another male occupant was transported from the scene and remains in a critical condition.

Police, emergency services, Rural Fire Service personnel and the Crash Investigation Unit attended the accident, with the highway closed in both directions at around 10.15pm last night.

Tools, acetylene welding gear, and debris were scattered across a large section of highway, which remained closed Sunday morning.

All eastbound traffic from Moree is being diverted along the Newell Highway to Narrabri and the Kamilaroi Highway to Walgett.

All westbound traffic from Walgett is being diverted along the Kamilaroi Highway to Narrabri and the Newell Highway to Moree.

Just after 10pm yesterday, emergency services were called to the Gwydir Highway, near Collarenebri, about 140 kilometres west of Moree, following reports of a crash.

Officers attached to Central North Police District attended and found a Toyota Hilux utility had rolled, ejecting the occupants.

Police and Rural Fire Service personnel commenced CPR on one occupant. However, he was unable to be revived. The 24-year-old man died at the scene.

A second man, aged 20, was treated by NSW Ambulance paramedics before being taken to hospital in a critical condition.

A crime scene has been established and investigations by the Crash Investigation Unit have commenced.

Gwydir Highway is still closed in both directions and motorist are urged to avoid the area. Investigations are ongoing.

Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au.

Information is managed on a confidential basis.

The public is reminded not to report information via NSW Police social media pages.

UPDATED: Gwydir Highway was reopened at 5.15pm, Sunday, December 28.