In a statement, the department said that ABP Food Group, who operate the plant, had indicated that none of the meat had entered the food chain.
The investigation is focusing on the full supply chain including the meat trader concerned and others who facilitated the purchase of the product and its transfer to users in Ireland.
Traces of horsemeat were found in processor Silvercrest, also managed by the ABP Group.
DNA was also discovered in food suppliers Liffey Meats and Dalepack Hambleton.
More top news
Low pressure keeps our weather unsettled into the weekend
A Royal Marine from Northern Ireland who built explosives for an Irish republican paramilitary group had 43 hides, a court has heard.
A gay man has spoken of pain he suffered as a young boy when doctors gave him chemicals and electric shocks in attempt to 'cure' him.