Irish Taoiseach Enda Kenny has committed to resolving the horse meat crisis after food safety chiefs warned of fraudsters drip-feeding contaminated product into the food chain.
As the scandal spread to more processors, the Republic of Ireland's fraud squad has been called in to help agriculture authorities track down the source of the mislabelled meat.
"This is a matter of reputation, obviously we cannot afford to have that," Mr Kenny said. "It is a matter that needs to be sorted out and it will be sorted out."
Rangeland Foods in Co Monaghan was one of the latest plants shut down after a sample at the factory tested positive with a reading of 75% horse DNA in raw ingredient, authorities said. It supplies burgers to one of Ireland's most popular fast food chains, Supermac's, but the restaurant's chief executive Pat McDonagh has insisted he is sure all his burgers are 100% Irish.
The highest level of horse has been found in a quantity of frozen meat being stored in Northern Ireland.
Freeza Meats in Newry had meat which was 80% horse, which the Food Standards Agency (FSA) said was potentially linked to the Silvercrest factory in the Republic of Ireland, one of the first processors to be named in the scandal. The meat has not entered the food chain.
The same meat trader in Ireland has supplied meat to Freeza, Silvercrest and Rangeland, the Food Safety Authority of Ireland (FSAI) said. The source has been blamed on a meat supplier in Poland. Professor Alan Reilly, whose research at the FSAI first exposed the contamination of processed beef burgers in Irish-made products, is due to brief a parliamentary committee on the controversy later.
The horse meat test results from Newry were made public just a day after food distributor 3663 identified Northern Ireland-based company McColgan Quality Foods Limited as the source of a "very small number" of halal savoury beef pastry products, which it supplied to prisons, that were found to contain pig DNA.
Northern Ireland's First Minister Peter Robinson also voiced concern on the potential impact on export trade. He said Northern Ireland produce was an attractive product in overseas markets.
"The attraction of that is the agricultural products from Northern Ireland are always regarded as being of the highest standard and if there is a view, whether it is pork going into halal meat or whether it's a case of some further drop in standards, then it has an impact on the whole of the agri-food industry," he said. "We have the highest standards and it is unfortunate that this has happened."