Police responded to the theft of a vehicle from a motorist on the M11 between j7 and j8 at Hatfield Heath yesterday morning just before 9.10am.
The stolen vehicle is a white Mercedes Sprinter van which was travelling northbound.
The helicopter assisted officers on the ground in a search for the vehicle.
The driver and his passenger were unharmed but the suspects, believed to be four men who are described as being armed with a firearm and purporting to be police officers, were travelling in a silver Ford Mondeo.
Anyone who sees either of these vehicles is asked to report that sighting to Essex Police via 101 immediately.