PARIS -- The price, smell and colour should have been clear tipoffs something was wrong with shipments of horsemeat that were fraudulently labeled as beef, French authorities said Thursday. The economy minister pinned the bulk of the blame on a French wholesaler at the heart of the growing scandal in Europe.

Britain's food regulator, meanwhile, said 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."

In Paris, Benoit Hamon, the economic and consumer affairs minister, said it appeared that the fraudulent sales had been going on for several months, and reached across 13 countries and 28 companies. He said there was plenty of blame to go around, but most of it rested with Spanghero, a wholesaler he said was well aware that the cheap meat was mislabeled when it sold it to Comigel, the frozen food processor.

"Spanghero knew," Hamon said. "One thing that should have attracted Spanghero's attention? The price."

Hamon said the mislabeled meat from Romania was far below the market rate for beef. Spanghero was to be suspended immediately and the results of the investigation have been forwarded to prosecutors, officials said.

A representative for Spanghero did not immediately return a phone call seeking comment. In a statement earlier this week, Spanghero said it does not buy, sell or process horsemeat. The company said it was co-operating with the investigation and would sue whoever was responsible for the fraud.

Comigel itself was not blameless, Hamon said. The paperwork had significant irregularities, including failure to specify country of origin.

"And once the meat was defrosted, we can ask ourselves why Comigel didn't notice that the colour and odour was not that of beef," Hamon said.

Britain's Food Standards Agency said eight out of 206 horses it checked had tested positive for phenylbutazone, commonly known as bute. It said of those eight, six -- all slaughtered by a firm in southwest England -- were sent to France and "may have entered the food chain."

The agency said it was working with French officials to trace the meat.

Thousands of meat products are being tested for the drug, and for horse DNA, after horsemeat was found in food products labeled as beef across Europe.

Pan-European police agency Europol is co-ordinating a continent-wide fraud investigation amid allegations of an international criminal conspiracy to substitute horse for more expensive beef.

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, which have a culture of eating horsemeat.

The scandal has uncovered the labyrinthine workings of the global food industry, where meat from a Romanian slaughterhouse can end up in British lasagna by way of companies in Luxembourg and France.

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

Britain's chief medical officer, Sally Davies, insisted that horsemeat containing the drug -- which is banned for human use in countries including Britain and the U.S. -- "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" anyone eating horsemeat would experience them.

"If you ate 100-per cent 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."

Peter Lees, emeritus professor of veterinary pharmacology at the Royal Veterinary College, agreed there was little risk of harm from eating horsemeat. He said that even the worst-case scenario involved a tiny amount of bute in a small percentage of meat samples.

"The risk of getting aplastic anemia that is posed by consuming a horsemeat burger is very low indeed," Lees said.

Nonetheless, the development heightened concerns about the security of Europe's food system.

Food Standards Agency head Catherine Brown said that before the current crisis, the agency had tested about 5 per cent of the horses slaughtered in Britain -- and about 6 per cent of those had shown traces of bute.

"That would say there has been a significant amount of carcasses with bute in going into the food chain for some time," she said.

Britain's Food Standards Agency said it had begun testing all horses slaughtered in Britain for bute, and that none would be exported for consumption unless they tested negative. The agency previously tested only a small percentage of slaughtered animals, which has fueled criticism of its failure to catch the horsemeat contamination sooner.

A "horse passport" system, which records whether animals have been treated with bute, is meant to stop the drug entering the human food chain.

On Thursday, 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.

The trail of illicit horsemeat stretching across Europe spread still further Thursday when Rangeland Foods, a processing factory in Ireland, said it had withdrawn some batches of burger products which contained beef supplied from Poland after it tested positive for up to 30 per cent 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.

Processed food containing horsemeat has also surfaced in Germany, where two national supermarkets have pulled frozen lasagna from their shelves.