(Adds comments from Irish prime minister)
DUBLIN, Dec 10 (Reuters) - Used oil from electrical transformers may have caused the dioxin contamination in animal feed that has led to an international recall of Irish pork products, the Irish Times reported on Wednesday.
Earlier this week, more than 20 countries cleared their shelves of Irish pork after dioxins up to 200 times the legal levels were found on 10 pig farms.
The Irish Times, without citing sources, said the contamination may have been caused by waste oil originating in Northern Ireland that should have been stored or destroyed.
The farm ministry said it was not in a position to comment on its investigations into the contamination. Ireland's Environmental Protection Agency, which is assisting the ministry in the probe, also declined to comment.
The crisis escalated further on Tuesday, when authorities said three cattle herds in Ireland were contaminated with dioxins.
Ireland, one of the world's top five beef exporters, said there was no need to recall any Irish beef products because the level and extent of contamination in the affected animals was much lower than the levels discovered at the pig farms.
Ireland's chief veterinary officer, Paddy Rogan, will confirm to EU counterparts in Brussels on Wednesday that Irish beef is safe and can continue to be traded normally on both domestic and export markets, the farm ministry said in a statement.
"We are facing yet another big challenge for the beef industry," Aidan Cotter, chief executive of Ireland's food board said on Wednesday.
Worries for Ireland's pig meat industry continued to grow as processors have refused to reopen their slaughterhouses until they get compensation for the loss of trade.
Talks between the processors and government resumed on Wednesday and Prime Minister Brian Cowen said progress had been made.
"I remain confident of achieving an outcome that will facilitate the early resumption of processing," Cowen told deputies during a parliamentary debate.
"We are acutely aware of the impact that suspension of slaughtering has had on the hundreds of producers throughout the country and the thousands of workers whose jobs have been compromised by recent events."
Farmers said a return to production was vital.
"If you go out to the supermarket shelves this morning they are being replaced with imported produce," said Tim Cullinan, head of the Irish Farmers Association's pigs committee.
Cullinan said stocks were building up on farms.
"We need to move 50,000 to 60,000 pigs into the processing plants on a weekly basis," he told public broadcaster RTE.
"We seem to be literally the meat in the middle of the sandwich here," he said. "We want to be back out on our farms and running our business." (Reporting by Jonathan Saul; editing by Karen Foster)