Five men have been arrested in counties Armagh, Monaghan and Tyrone as part of a cross-Border investigation into an animal feed dioxin contamination in 2008.
The contamination led to the recall of all Irish pork products in December 2008 at a cost of more than €180 million.
Gardaí arrested one man aged in his 50s and he is currently being held at Monaghan Garda station under Section 4 of the Criminal Justice Act.
Four other men (aged 25, 27, 29 and 43) were arrested by the PSNI - three in Co Tyrone and one in Co Armagh - on suspicion of fraud by false representation. They have been taken to the crime suite at Antrim PSNI station for questioning.
The contamination in 2008 resulted in a recall of all Irish pork products after pig meat on several farms was found to have between 80 and 200 times more dioxins than the recognised safety limit.
Dioxins such as polychlorinated biphenyls (PCBs) were detected in the biscuit feed meal for pigs and cattle.
Many animals were slaughtered, and compensation costs for Ireland alone are estimated at more than €180 million.