The gang steals diggers, trailers and even lorries on one side of the Border and then tries to sell them on the other side.
Detectives believe that the gang responsible may be stealing to order.
In the latest twist in the investigation Gardai have asked the PSNI for help in tracing tens of thousands of euro worth of equipment taken in Co Donegal earlier this month.
A Ford Iveco lorry and trailer were stolen along with a Hitachi digger from Letterkenny on April 5. The lorry has a white cab and a black body.
The theft of farm machinery and lorries has grown substantially in both jurisdictions, we have been told.
A range of farm machinery stolen in England and the North and offered for sale in the North West were seized last autumn.
These included top of the range John Deere, Massey Ferguson and New Hollands tractors as well as slurry spreaders and even a baler.
In a number of cases vehicle identification numbers were removed from the tractors and replaced with numbers copied from older vehicles.
We understand some of the tractors were offered for sale via the internet at lower than usual prices and detectives are checking several other cases in the west and north west.