Police in the U.K., meanwhile, announced the arrests Thursday of three men on suspicion of fraud at two meat plants inspected earlier this week by the country’s Food Standards Agency.

The two separate developments were part of an escalating scare that has raised questions about food controls in the European Union — and highlighted how little consumers know about the complex trading operations that get food from producers to wholesalers to processers to stores and onto their dinner table.

Europol, the European Union police agency, is coordinating a broad continent-wide fraud investigation amid allegations of an international criminal conspiracy to substitute horse for more expensive beef.

In Paris, Benoit Hamon, the government’s consumer affairs minister, said it appeared that in the most prominent case fraudulent meat sales had been going on for several months, and reached across 13 countries and 28 companies. He did not name the countries or companies.

He said there was plenty of blame to go around, but most of it rested with Spanghero, a wholesaler based in southern France.

Officials at Spanghero denied knowingly buying and reselling horsemeat but French authorities immediately suspended their trading activities.

Hamon said Spanghero was one company in a chain that started with two Romanian slaughterhouses that says they clearly labeled their meat as horse.

The meat was then bought by a Cyprus-registered trader and sent to a warehouse in the Netherlands.

Spanghero bought the meat from the trader, then resold it to the French frozen food processor Comigel. The resulting food was marketed under the Sweden-based Findus brand as lasagna and other products as containing ground beef.

Hamon said Spanghero was well aware that the meat was mislabeled when it sold it to Comigel.

“Spanghero knew,” Hamon said. “One thing that should have attracted Spanghero’s attention? The price.”

Hamon said the meat from Romania cost far below the market rate for beef.

A representative for Spanghero said company officials have been interrogated by authorities, who have raided Spanghero headquarters several times in recent days, but no one has been arrested.

The representative insisted the company acted “in good faith” and that it never knew the meat it bought and sold was horsemeat. The representative said he was not authorized to be publicly named according to his contract with Spanghero.

He wouldn’t comment on French authorities’ insistence that Spanghero should have recognized the meat as horse by its price, smell and color.

Food processor Comigel was not blameless either, Hamon said, declaring that the paperwork from Spanghero had significant irregularities, including a failure to specify country of origin.

“And once the meat was defrosted, we can ask ourselves why Comigel didn’t notice that the color and odor was not that of beef?” Hamon said.

Romanian food suppliers rejoiced that the blame for the frozen lasagna scandal has shifted away from Romanian slaughterhouses to companies in France — a country that prides itself on its cuisine and culinary culture and isn’t usually caught up in food scandals.

Sorin Minea, the chief of Romalimenta, the Romanian food industry association, urged tough sanctions for the French companies. “Romania, small and ugly as it, respected all European legislation. In the U.K., legislation was not respected,” he said. “I am sad that first we were accused and then there was an inquiry. We feel we are not part of the European family.”

Britain’s food regulator, meanwhile, said Thursday that six horse carcasses that tested positive for an equine painkiller may have entered the human food chain in France and that horsemeat tainted with the medicine may have been sold to consumers “for some time.”

The U.K. Food Standards Agency said eight out of 206 horses it checked had tested positive for phenylbutazone, commonly known as bute. The drug is banned for human use in countries including Britain and the U.S.

Almost no horsemeat is consumed in Britain, where hippophagy — eating horses — is widely considered taboo. But thousands of horses killed in the country each year are exported for meat to countries including France and Belgium that have a culture of eating horsemeat.

The scandal has also raised the uncomfortable idea that Europeans may unwittingly have been consuming racehorses, which are often treated with bute.

Britain’s Aintree race track said a slaughterhouse in northern England shut down this week by government investigators had a contract to dispose of fatally injured racehorses. The racecourse said it was “as confident as we possibly can be” that none of the meat had entered the human food chain.

Despite the ban on bute for humans, Britain’s chief medical officer, Sally Davies, said that horsemeat containing the drug “presents a very low risk to human health.”

Davies said the drug was once prescribed to patients with severe arthritis, and while it sometimes produced serious side effects including the blood disorder aplastic anemia, it was “extremely unlikely” that anyone eating horsemeat would experience them.

“If you ate 100-percent horse burgers of 250 grams (8.8 ounces), you would have to eat, in one day, more than 500 or 600 to get to a human dose,” she said. “It would really be difficult to get up to a human dose.”

In other, separate developments in the multi-tentacled horsemeat scandal Thursday:

— Police in Wales said two men — ages 64 and 42 — were arrested at Farmbox Meats near Aberystwyth, in Wales, while a 63-year-old man was arrested at the Peter Boddy Slaughterhouse in Todmorden, West Yorkshire.

—Germany said food containing horsemeat has also surfaced there, as two German national supermarkets have pulled frozen lasagna from their shelves.

—In Ireland, where fears about undeclared horsemeat first surfaced earlier this year, processing factory Rangeland Foods said it had withdrawn some batches of burger products that contained beef supplied from Poland after it tested positive for up to 30 percent horse meat. Food Safety Authority of Ireland said the products had been sold to the catering and wholesale sectors and distributed to Ireland, Britain, Spain, France, Germany and the Netherlands.

—In Britain, supermarket chain Asda said it was withdrawing a beef Bolognese sauce from its shelves after tests indicated the presence of horse DNA and would pull three other products from the same supplier as a precaution. The company previously has withdrawn four other products which tested positive for horse DNA.

—In the Netherlands, the Economic Affairs Ministry said Thursday the country’s Food Safety Authority is carrying out a large-scale investigation in coming weeks and plans to inspect some 100 companies from slaughterhouses to supermarkets and take 200 samples including meat cuttings, mincemeat and other prepared food. The authority also is investigating labeling at 40 companies, identifying meat and checking paperwork.