They included lasagna sold by frozen food giant Findus and spaghetti bolognese sold by UK supermarket giant Tesco, both made by French supplier Comigel.

The industry was already reeling from a bombshell last month, when Irish investigators found horse and pig DNA in a number of hamburger products.

Investigations are under way in France, Sweden and Britain.

In Romania, Prime Minister Victor Ponta said Monday that the two slaughterhouses in the country that were initially suspected to have links to the horse meat scandal never had direct contact with Comigel and have done nothing illegal.

"This tendency to throw the responsibility as far away as possible, eventually to the new members (of the European Union), to countries that might have a weaker PR policy, is something that bothers me," he said.

Minister of Agriculture Daniel Constantin said there was no evidence of mislabeling in Romania.

Comigel has not responded to CNN's requests for comment. But CEO Erick Lehagre told French news agency Agence France-Presse on Sunday that a French supplier "fooled" his company. "We were victims," he told AFP.

This month, Britain's National Beef Association called for more specific labeling of meat products and asked that labels bear the words "United Kingdom origin."

British food companies have been told to test their beef products for "authenticity" and report back to authorities by Friday.

British supermarket chain Waitrose said Wednesday that it had "in recent weeks" removed from its shelves frozen meatballs labeled as beef after tests indicated that two batches may have contained pork.

But tests revealed no horse meat in its meatballs or frozen beef burgers, it said.

In the United States, Congress effectively prohibited the slaughtering of horses for human consumption in 2007, by denying the use of federal funds to inspect horses destined to become food, a 2011 Government Accountability Office report said.

The legal maneuver does not preclude horse owners from selling to slaughterhouses in Canada and Mexico, and the GAO said in a report that many Americans have taken advantage of that opportunity.

"From 2006 through 2010, U.S. horse exports for slaughter increased by 148 and 660% to Canada and Mexico, respectively," the report said. "As a result, nearly the same number of U.S. horses was transported to Canada and Mexico for slaughter in 2010 -- nearly 138,000 -- as was slaughtered before domestic slaughter ceased."