The appeal comes as police continue their search for the culprit following the violent incident in the Hunter earlier this month.

Police said a 20-year-old man was delivering a package at Oakfield Road, Woodberry, about 10.45pm on May 8 after an online sale.

When he arrived at the pre-arranged spot, a car stopped behind his vehicle.

A man approached the driver's side door, identifying himself as a police officer - though he was not dressed as one.

The man reached into the vehicle and tried to take the keys out of the ignition - he was unsuccessful, but allegedly assaulted the 20-year-old and took the package from the back seat.

Police said he then fled in the car.

The Newcastle Herald understands the package contained nitrous oxide.

Also known by the street name 'nangs', the gas is classified as a Schedule 4 drug and is a restricted substance, which can have psycho-active effects if misused.

However, there are some legal uses for nitrous oxide - including to whip cream for baking.

The man who allegedly impersonated the police officer is described as being of Caucasian appearance, aged in his 30s, with a tattoo on the front of his neck, wearing a grey hooded jumper and dark tracksuit pants.

Anyone with information that could help police with their investigation is being asked to contact Maitland Police Station on 4934 0200 or Crime Stoppers on 1800 333 000.

While you're with us, did you know the Newcastle Herald offers breaking news alerts, daily email newsletters and more? Keep up to date with all the local news - sign up here

IN THE NEWS: