Some 16 vehicles were found at a property in the Crossan Road area of Newry on Monday afternoon.
A number of cars - including BMW, Volkswagen, Citroen, Mercedes, Chrysler and Saab - were seized
Several are believed to have been stolen, with two BMWs confirmed as stolen in the Republic.
A lorry, tools, engine parts and documents have also been seized by police. Enquiries will now begin to identify the owners of the vehicles.
PSNI detective inspector Will Tate said the force would "now begin the task of identifying and locating owners of the vehicles seized to ascertain if they were in these premises lawfully or unlawfully".
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