The scandal over horse meat sold as beef has now spread to 16 countries across Europe as an abbatoir in Romania was pinpointed for the source of at least some of the falsely labelled product.
Up to now, the focus of Irish investigators had been on Polish meat processors.
However, it has now emerged that horse meat found in Findus and Aldi frozen ready meals originated in Romania.
French firm Comigel, which produced the lasagnes and spaghetti bolognese products, said it has established that one of its suppliers bought meat from a Romanian producer who used abattoirs where both cattle and horses were slaughtered.
The meat came to Romania through a dealer in Cyprus, working through another dealer in Holland, to a meat plant in the south of France, which sold it to a French-owned factory in Luxembourg, which made it into frozen meals sold in supermarkets in 16 countries.
A spokesman for Agriculture Minister Simon Coveney said that "all avenues" of investigation are now being looked at.
"The investigation is spreading all the time. It's in the hands of the SIU (Special Investigation Unit) who are liaising with the gardai," he added.
He said testing of meat products for horse DNA was being done on an "ongoing basis".
The spokesman added that there are no immediate plans to summon Irish retailers for a crisis meeting similar to that held in the UK at the weekend.
British Environment Secretary Owen Patterson met a group of UK retailers, many of which have a presence in Ireland, to discuss the horse meat scandal. The supermarkets agreed to step up their testing regime and were ordered to publish these results to shore up consumer confidence.
The affected Findus and Aldi products are being tested for phenylbutazone, an anti-inflammatory medicine used to treat horses, which is prohibited from the food chain as it may pose a risk to human health.
The Food Safety Authority of Ireland is advising consumers who have bought the products not to eat them but to return them to shops.
Meanwhile, the French fraud office is launching its own horse meat investigation after Comigel, one of Europe's biggest food producers, was dragged into the scandal.
French Consumer Minister Benoit Hamon said that investigators had uncovered the Byzantine route taken by the 'fake' beef, from Romania via Cyprus, Holland and France.
Comigel said it had traced the horse meat to one of its suppliers – Spanghero, based in south-west France. Spanghero has said it will issue legal proceedings against its Romanian supplier and said it believed it was buying beef.