Eight people were being questioned today after police disrupted a stolen motor caravan network operating between Britain and Ireland.
They were arrested after a three-month probe into a racket which has left victims hundreds of thousands of pounds out of pocket.
Chassis details on the mobile homes were being switched in a bid to avoid detection, a senior Police Service of Northern Ireland officer involved in the investigation revealed.
Superintendent Tony Weston said: "The scam is very detailed and has caught a number of people by surprise.
"The unsuspecting buyer has been conned into believing the vehicle they are purchasing is legitimate, as the vehicles in question are being sold with authentic documentation."
A large theft and ringing network was detected between Britain, Northern Ireland and the Irish Republic, police said. Details were passed on from England before the suspects were held, according to Mr Weston.
He added: "The scam has resulted in individuals from Northern Ireland losing over £500,000, which for some, has been their life savings.
"To date we have made eight arrests for handling stolen goods and the investigation is still ongoing."
Police also urged the public to be alert when buying a motor caravan.
They were warned to avoid cash payments, confirm the seller's identity, check for damaged locks, make sure keys fit, and be wary if the vehicles are advertised below market value.