Police in the North are investigating a second hand car sales scam in which stolen vehicles are being sold with bogus registration papers.
The Department of Environment's Driver and Vehicle Licensing NI told people buying a second hand car to be careful it is not stolen.
At least four cases have been identified recently, and more in the Republic, where people have purchased what turned out to be stolen vehicles.
In the northern cases sellers advertised giving only a mobile phone number, offered to bring the vehicle to a mutually convenient point such as a well-known roundabout, and usually asked for payment in cash.
The vehicles purchased were cloned - given the registration mark of a vehicle of identical model and mark. Some also had what appeared to be a genuine vehicle log book.
Investigators from the DVLNI have identified that some had books from a batch recalled for destruction following changes to vehicle taxation in March 2001, said the department.
Other vehicles had quality forged registration books. The PSNI is now investigating both forms of fraud.
Mr Brendan Magee, chief executive of the DVLNI, said anyone buying a used car privately should take practical steps to limit the chances of being sold a stolen vehicle.