London (CNN) -- Three horse carcasses tainted with a veterinary drug harmful to humans have "probably" entered the food chain, France's agriculture minister confirmed Saturday.
The three carcasses are among six flagged up by UK authorities earlier this month as having tested positive for the drug phenylbutazone, also known as bute, after they were shipped to France.
The faint traces of bute found in these carcasses "do not pose a risk to health," Agriculture Minister Stephane Le Foll said.
The news is the latest to cast a shadow on the European meat industry, which has been rocked in recent weeks by the discovery of horse meat in products labeled beef across a raft of countries.
The horse carcasses tainted with bute were legally slaughtered in Britain but should not have entered the food chain, the UK Food Standards Agency said.
The testing process has now been changed to ensure that horse meat can only be shipped out of abbatoirs after it's given the all-clear for bute, the Food Standards Agency said.
UK chief medical officer Sally Davies sought earlier this month to reassure people worried about the health impact of eating food contaminated with the drug, used as a painkiller in horses.
"It's understandable that people will be concerned, but it is important to emphasize that, even if bute is found to be present at low levels, there is a very low risk indeed that it would cause any harm to health," she said.
A survey of UK consumers last week indicated that about one in four adults will buy less processed meat as a result of the scandal, and that one in five have started buying less meat generally.
More than two-thirds of those polled by Consumer Intelligence said their trust in food labeling had been eroded. The online survey of more than 2,200 adults was conducted February 14 to 15.
France's President Francois Hollande called Saturday for mandatory labeling to be introduced for meat in processed meals, so that "consumers know the origin of the products they are consuming, especially meat."
Authorities suspended operations at a meat processing plant in Ireland on Friday after inspectors found it was exporting horse meat to the Czech Republic under a label in the Czech language which translated as beef.
Ireland's Agriculture Minister Simon Coveney said he was seriously concerned by the development, which has been reported to police.
The French Agriculture Ministry said Friday that the license of a French meat-processing plant implicated in the scandal, Spanghero, remained suspended.
Meanwhile, frozen food giant Birds Eye confirmed that testing had revealed the presence of horse DNA in a chilli con carne product sold in Belgium and produced by Frigilunch.
"In accordance with our high standards, we are immediately withdrawing this product from sale in Belgium," Birds Eye said in a statement. Other products made by the same supplier have been withdrawn from UK and Irish supermarkets as a precaution, it said.
Food manufacturer Sodexo also said it was withdrawing "all frozen beef products from its UK catering operations with immediate effect," following the discovery of horse DNA in some products. "This situation is totally unacceptable," it said in a statement.
Sodexo supplies food to British schools and the armed forces, among other clients.
The UK Food Standards Agency released the results Friday of a second round of testing, which found six new beef products that tested positive for horse meat. A first round of testing, completed a week earlier, found 29 beef products that contained horse DNA.
The meat industry was first thrust into the spotlight last month when Irish investigators found horse and pig DNA in hamburger products. The discovery of pig DNA is of particular concern to Jews and Muslims, whose dietary laws forbid the consumption of pork products. Jewish dietary laws also ban the eating of horse meat.