It's emerged that the trader's firm, McAdam Foods, bought Polish beef which contained up to 80pc horse.
The company has been named as a supplier to two companies which sold beef products which contained significant levels of horse DNA.
McAdam Foods has now been plunged into the centre of the international scandal and is assisting gardai in the probe.
Agriculture Minister Simon Coveney is adamant that the presence of horsemeat in Irish beef burgers is not accidental, adding that he has invited Polish authorities to Ireland as part of the investigations.
But the saga took a new twist yesterday when it emerged that the Monaghan-based McAdam Foods supplied meat to companies already embroiled in the controversy.
One of these companies is Rangeland Food – which earlier this week found that 75pc of its product contained horse.
And Silvercrest Foods, which lost its lucrative Tesco contract, also purchased materials from McAdam Foods.
Responding to the revelation that his firm is now at the centre of the scandal, Mr McAdam said he is an "innocent victim" and that he had "absolutely not" imported the product because it was cheaper.
He said that he and his firm is co-operating fully with the Food Safety Authority of Ireland (FSAI) and the Department of Agriculture.
Meanwhile, Mr Coveney laid the blame at a Polish supplier when addressing an Oireachtas committee.
He said that there was a "complex web" in the supply chain to factories.