Six horses slaughtered in the U.K. that tested positive for a potentially harmful drug were exported to France and may have entered the human food chain, Britain's Food Standards Agency said Thursday.
Phenylbutazone, commonly known as bute, is an anti-inflammatory painkiller for sporting horses but is banned for animals intended for human consumption.
Britain's food regulator said it was gathering information on the six carcasses sent to France and will work with the French authorities to trace them.
The FSA said it checked 206 horse carcasses between Jan. 30 and Feb. 7. Of these, eight tested positive for the drug.
It said the six sent to France were slaughtered by a firm in Taunton, western England. The remaining two did not leave the slaughterhouse in Nantwich, north west England, and have now been disposed of.
The FSA introduced 100 percent testing of horse carcasses on Jan. 30 in response to the growing horse scandal.
The issue first came to light on Jan. 15 when routine tests by Irish authorities discovered horsemeat in beef burgers made by firms in Ireland and Britain and sold in supermarket chains including Tesco, Britain's biggest retailer.
Concern grew last week when the British unit of frozen foods group Findus began recalling its beef lasagne on advice from its French supplier, Comigel, after tests showed concentrations of horsemeat ranging from 60 to 100 percent.
Meanwhile in France, an investigation into how horsemeat found its way into prepared meals in Europe discovered that a French processing company called Spanghero sold what could have been horsemeat as beef, officials said Thursday.
"It would seem that the first agent in this chain to label the meat 'beef' was indeed Spanghero," Consumer Affairs Minister Benoit Hamon told a news conference of the company based in the southwestern town of Castelnaudry.
"The investigation shows Spanghero knew the meat labeled as beef could be horse. There was a strong suspicion," he said, arguing that Spanghero could also not have failed to notice that the meat in question was much cheaper than beef.
In an emailed statement, Spanghero denied the accusations and said it firmly believed that what it was selling was beef.
Agriculture Minister Stephane Le Foll said the government was considering withdrawing Spanghero's operating license.
The investigation found the company had generated a profit of 550,000 euros ($733,800) over six months by selling cheap horsemeat as beef, Hamon said.