A police sergeant on his way to help colleagues involved in a car chase has been killed in a crash in New South Wales Hunter Valley.

Sergeant Geoffrey Richardson, 43, was driving his patrol car when it veered off Lovedale Street at Allandale and hit a tree late on Saturday night.

He was on his way to help colleagues involved in a car chase when the accident happened.

Paramedics were called but Sergeant Richardson, who worked at the Port Stephens Local Area Command, died at the scene.

He was the only person in the vehicle.

NSW Police Commissioner Andrew Scipione, who has travelled to the region, said the force had lost a "very good man" in the tragedy.

"I have had a chance to meet with his family and certainly paid my condolences to his wife Margaret and his children," Commissioner Scipione said.

"It is a terribly sad event, we've lost a very good man.

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"He was respected, he was loved, and certainly he was one of our finest, and NSW is a much poorer state as a result."

The accident is now the subject of a critical incident investigation to be conducted by Newcastle Local Command, Commissioner Scipione said.

"The officer was not involved in a pursuit, he was on his way to assist others that were involved in a pursuit," he said.

Commissioner Scipione said support would be provided to Sergeant Richardson's family, including his wife who was also a senior constable in the police force.

"My heart goes out to his family, we'll do all we need to to make sure that they're looked after, because they're a really important part of our [policing] family," he said.

Police have appealed for witnesses to come forward.

In a tribute released to media, police said Sergeant Richardson provided "18 years of dedicated and distinguished service to the people of NSW".

"He was the recipient of numerous awards, including a Regional Commander's Commendation for Bravery after he arrested a number of offenders while off-duty at Nelson Bay in 2012," the statement reads.

He was a loving and loved husband and father, the statement reads, who leaves behind a "devastated" family.