Motorists are being targeted by fraudsters claiming they have run out of petrol and need money.
Cambridgeshire police received 12 reports between January 26 and February 3 of a man flagging down vehicles and asking for money for petrol.
The fraudster then hands over a business card and gold jewellery as a guarantee to pay them back.
On occasion, the man has accompanied the victim in their car to a petrol station, with another man, sometimes two in another car.
A silver Vauxhall Vectra, a red Saab convertible, silver and green Volkswagen Passats and a white BMW have been used in the scam.
So far, the fraud has been carried out at numerous places across the county, including near the A14 at Brampton and Godmanchester.
The man is described as of Middle Eastern appearance, between his late 40s and early 60s, between 5ft 4in and 5ft 8in and heavy build.
INFORMATION: Anyone with information should contact police on 101 or Crimestoppers, anonymously, on 0800 555 111.