The Food Safety Authority of Ireland has ordered the withdrawal and recall of all Irish pork products dating back to 1 September.
It follows the discovery of a contaminant in pig feed by a dioxin known as PCB at levels between 80 and 200 times the safe limits.
PCBs are highly dangerous man-made chemicals that were banned in 1979. They effect the immune and reproductive systems and can, in certain cases, cause cancers.
They can still be found in certain products made before the ban came into force.
The contamination first came to light last Monday, but the positive tests in the pork was only confirmed this afternoon.
The public have been advised to destroy all pork products
purchased since September.
Contaminated feed was used at a total of 47 farms.
Nine of these were pork producing farms. The remaining 38 were beef farms, with one of those also producing pork products.
But the FSAI has advised that it is not necessary at this time to have a similar withdrawal of beef products.
Alan Reilly of the FSAI said a whole range of products, including sausages, bacon, pizza toppings, should be destroyed.
He urged consumers to return Irish pork products to retailers if possible or simply put them in the bin.
The Taoiseach and Minister for Agriculture Brendan Smith, have attended crisis talks at the Department of Agriculture following the discovery of the toxic substance in slaughtered pigs.
The discovery has provoked concern in the farming community.
The pork industry is the fourth biggest in the agriculture sector and is worth around €400 million per year.
The movement of animals at some 30 farms has been restricted.
A major investigation has been launched by the Department of Agriculture and the Food Safety Authority.
Restrictions on pig production units
Minister of State for Food Policy Trevor Sargent said the Government had acted swiftly to deal with the situation.
Mr Sargent said the affected animal feed had been banned and the pig production units using it had been restricted.
He said he would be working with An Bord Bia to ensure that quality pigmeat products - including those organically certified - can be brought back into the market as quickly as possible.
Meanwhile, Labour’s spokesperson on agriculture and food Sean Sherlock, has called for a full account of the extent of the risk to human health.
Fine Gael’s spokesperson on agriculture, Michael Creed described the discovery as potentially the biggest threat to the agri-food sector since the outbreak Foot & Mouth disease.
Chief Medical Officer says move is precautionary
The state's Chief Medical Officer said there was no need for the public to worry and that the government had taken a precautionary approach to minimise the risk to public health.
Dr Tony Holohan said the public should simply destroy what pork products they have in their fridge and freezer.
He said the dioxin is only dangerous if a person is exposed to it over a long period of time. In such circumstances, he said, it can have a range of effects on organs such as the liver and nervous system.
But he stressed that the period in question here is much shorter, and such effects should not arise as the exposure has been identified at an early stage.
Dr Holohan said because there is no risk from the low exposure, people do not need to seek medical help.