The pigs may have been contaminated by animal feed
Pork from the Irish Republic and Northern Ireland should not be eaten because of fears of contamination, the UK's Food Standards Agency has said.
The advice follows the recall of pork products after tests on slaughtered Irish pigs showed some pork products contained potentially harmful dioxins.
The FSA stressed consumers are unlikely to be at any "significant risk".
The Irish Republic's chief vet said contaminated pork products may have been exported to up to 25 countries.
Several other countries in Europe have issued alerts over the pork.
The FSA said: "Adverse health effects from eating the affected products are only likely if people are exposed to relatively high levels of this contaminant for long periods."
The source of the problem is suspected to have been contaminated oil.
The plant involved - Millstream Power Recycling Limited, in Co Carlow - said it was working with the Irish government as it investigated how the company's strict health and safety procedures could have possibly been breached.
A spokesman for the company - which recycles food products into pig meal - said the oil which officials were testing had never been added as an ingredient but was used in a machine used to dry animal feed.
Tests on the slaughtered Irish pigs showed some pork products contained up to 200 times more dioxins than the recognised safety limit.
The spokesman said production at the plant, which is owned by a Robert Hogg and employs around 15 people, was stopped earlier this week when it was first linked to the scare.
Consumers and retailers have been warned to destroy all Irish pork and bacon products bought since 1 September as a precaution.
Bacon, ham, sausages, white pudding and pizzas with ham toppings are also included in the withdrawal of stocks.
But food safety expert Professor Hugh Pennington told the BBC the health risk was "very, very low".
He said: "You have to have a lot of these compounds. You have to eat a lot of them, enormous amounts to have any visible effect."
The feed was also delivered to nine farms in Northern Ireland which are now under restrictions.
Lidl: removed 'own-brand' black pudding and pork belly products
Asda: removed all Irish-sourced pork products
Tesco: removed own-brand pork, bacon and sausages
Waitrose: precautionary removal of Paul Rankin branded sausages
Sainsbury's: no Irish pork used in fresh meat ranges.
Graham Furey, the president of the Ulster Farmers' Union, told BBC News he hoped the chemicals were not passed on to any Northern Irish animals.
He said although officials were inspecting "a number of premises" they had not yet found any positive signs of the dioxins in any of the meat from the province.
The British Retail Consortium said supermarkets across England, Scotland and Wales had withdrawn from sale "the very small proportion" of Irish pork they stocked following advice from the FSA.
Waitrose, Lidl and Tesco are among some of the supermarkets which have removed particular products and offered customers refunds.
Other supermarkets contacted by BBC News said they were continuing to check their supplies.
Dioxins are formed during combustion processes, such as waste incineration, and during some industrial processes.
Suspicions over contamination were first raised on Monday as a result of the routine testing of pigs, which indicated the presence of polychlorinated biphenyls (PCBs) - banned in the Irish Republic since the 1970s - in animal feed.
The chief executive of the Food Safety Authority of Ireland, Alan Reilly, said investigations were still under way into how the contamination got in to the animal feed.
He said: "It's more than likely from the types of dioxins that we have that it looks like some kind of industrial oil or industrial contaminant and we're trying to find out where that came from."
He added that culling of animals was likely in order to remove them from the food chain.
The Irish Agriculture Minister Brendan Smith said an investigation involving the Irish police was now under way into how the contaminated feed was given to pigs.
Chronic long-term exposure to dioxins can have serious health effects, including causing cancers, but Irish officials said the recall would ensure consumers only had minimum exposure to it.
Pork products from across Ireland should be avoided
The country's chief medical officer, Dr Tony Holohan, said anyone who had eaten pig meat did not need to seek medical help.
Mr Smith said the problem in the Republic was confined to 47 farms - including 38 beef farms.
Labour Party spokesman on agriculture and food, Sean Sherlock, said the government's priority had to be consumers but said the scare was a "threat to the viability of our food industry".
Irish Prime Minister Brian Cowen said action had to be taken to "reinforce" the public's confidence and allow the industry to "move on".
Padraig Walshe, president of the Irish Farmers' Association, said it was vital to trace the origins of the contamination.
He called the recall "a huge blow" and said the farmers were being punished despite buying their feed from a "licensed source".
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