LONDON - European supermarkets were ordered to clear their shelves of Irish bacon, ham and sausages yesterday after authorities announced that Irish pork products had been tainted with a potentially cancer-causing chemical.

Health officials across the continent warned their consumers not to eat Irish pork after the discovery of dioxins in Irish pigs and pig feed at 80 to 200 times the safety limit. Irish government officials described the recall - which affects all pig products produced since Sept. 1 - as a precautionary move, but farmers called it a nightmare for the industry.

Ireland's Food Safety Authority said the dioxin made its way into the food chain after pig feed from one producer was tainted with some sort of industrial oil. While only 10 percent of the country's pig meat was affected, that was processed and mixed in with other meat, resulting in widespread contamination.

Yesterday, the crisis spread to the United Kingdom as the government of Northern Ireland announced that nine farms in the province had used the same tainted feed.

"We're actually reeling in shock at the moment at the scale of this disaster," Tim Cullinan, an official with the Irish Farmers Association and a pig farmer, told Irish state radio RTE.

He said he believed authorities had identified the source of the contamination and hoped to get fresh pork back on the shelves within days. Meanwhile, he said, the recall had dealt a body blow to pig farmers and processors.

"It couldn't have come at worse time, the weeks leading up to Christmas. . . . It's a nightmare, to be honest," he said.

Tony Holohan, the Irish Department of Health's chief medical officer, urged people not to purchase or consume pork products, but stressed the move was precautionary.

"We're not anticipating significant health effects," he told RTE. His comments were echoed by Britain's Food Standards Agency, which said it did not see any significant risk to British consumers.

Ireland's farms produce more than three million pigs a year, nearly half of which are consumed within the Republic of Ireland. But Irish pork also is heavily exported to neighboring Northern Ireland and Britain - and appears in grocery stores and processed meats through much of Europe and Asia.

Last year Ireland exported 113,000 tons of pig meat, nearly half of that to the United Kingdom. Ireland also shipped more than 500,000 live pigs to the U.K. for slaughter and processing there.

Ireland's other major customers for pork are Germany, which bought 9,000 tons last year; France, Italy and several Eastern European countries, which together took more than 20,000 tons; Russia, 6,600 tons, and China, 1,100 tons.

Germany's ministry for consumer protection said yesterday that it had called on wholesalers and supermarkets to pull any Irish pork from their shelves, but said it was too early to say how much meat was involved. Similar warnings were issued by other European bodies.