A critical incident investigation has been launched following the fatal crash, which occured shortly before 10am.

At that time officers from Traffic and Highway Patrol were patrolling the Mitchell Highway, Narromine, about 45km west of Dubbo, when they observed a vehicle and turned around to follow it.

A short time later, police located the vehicle crashed off the roadway and hit a tree.

The male driver and sole occupant was located deceased inside the vehicle. He is yet to be formally identified.

A crime scene has been established and a critical incident team will now investigate all circumstances surrounding the incident.

That investigation will be subject to independent review and a brief will be prepared for the information of the Coroner.

No further details are available at this time however police are calling for witnesses to come forward.

Police are urging anyone with information in relation to this incident to call Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page: https://nsw.crimestoppers.com.au/

Information you provide will be treated in the strictest of confidence.

More details as they come to hand.