Horsemeat scandal: Bute found in eight horse carcasses
Eight horses, killed in the UK, tested positive for the painkiller bute and six may have entered the food chain in France, the Food Standards Agency said.
England's chief medical officer said the highest level detected was 1.9mg of bute per kg of horsemeat, which posed "very little risk to human health".
Testing started before horsemeat was discovered in processed beef products.
Earlier, food minister David Heath said tests on Findus beef meals found to contain horsemeat were negative.
The prime minister's spokesman said the UK was working very closely with the French authorities tracking the carcasses, which were identified on Thursday morning.
FSA rules which came into force this week mean all horsemeat in the UK should be tested for bute before it is allowed to be sold for food.
Tests on a sample of horse carcasses took place over a three-month period last year after intelligence from abattoirs suggested bute was present in the food chain. Some six per cent of the carcasses tested positive, prompting the FSA to start testing on all horse meat in January.
A total of 206 carcasses were examined between 30 January and 7 February and the eight with bute were discovered.
The FSA said six of the horses were slaughtered at LJ Potter Partners at Stillman's in Taunton, Somerset, and were exported to France, where horsemeat is regularly consumed.
The two killed at High Peak Meat Exports in Nantwich, Cheshire, did not leave the slaughterhouse and have been destroyed.
In a statement, LJ Potter Partners said all the horses it slaughtered had been accompanied by a horse passport issued by the government permitting entry to the food chain.
But it said it had warned the scheme "would not ensure public health" when drafted into law and also questioned "ineffective" EU regulations.
"We are seeking a fundamental reappraisal of the legislation to permit our legitimate industry to perform its dual role in protecting horse welfare and providing customers who wish to purchase and consume horsemeat with a product in which they can be confident," it said.
Concerns about horsemeat first came to light on 15 January when tests by Irish authorities found horsemeat in beefburgers made by firms in the Irish Republic and the UK and sold in supermarket chains including Tesco and Aldi.
A growing number of UK retailers have since recalled processed beef products found to contain horsemeat. And last week the British unit of frozen foods giant Findus started to recall its beef lasagne on advice from its French supplier, Comigel, after tests showed concentrations of horsemeat.
In other developments:
- The French processing company that supplied Findus sold meat labelled as beef despite knowing it could have been horsemeat, the French government has said. Spanghero had previously said it was a victim of its supplier but officials said it appeared the Romanian company had acted in good faith
- The European Union is urging member states to conduct random tests for horsemeat in processed beef products
- Horsemeat has been detected in frozen lasagne on sale in Germany and supermarkets have started removing the product from their shelves
- Beef has been removed from school meals across Staffordshire as a precautionary measure amid the horsemeat scandal
- In Wales, Conservative rural affairs spokeswoman Antoinette Sandbach has called for local authorities to test all meat entering the public sector food chain
- A meat processing factory in the Irish Republic, Rangeland Foods in County Monaghan, has withdrawn some batches of burger products which contained beef supplied from Poland - some of which were found to contain between 5-30% horsemeat
- A report from the Commons Environment, Food and Rural Affairs committee called for the FSA to have stronger powers to force meat producers to carry out testing
Chief medical officer Prof Dame Sally Davies said an individual would have to consume vast quantities of horsemeat containing bute to be at risk.
She said: "A person would have to eat 500-600, 100% horsemeat burgers a day to get close to consuming a human's daily dose. [The drug] passes through the system fairly quickly, so it is unlikely to build up in our bodies."
Bute is sometimes used as a drug to treat individuals suffering from a severe form of arthritis, but in rare cases it causes a serious blood disorder known as aplastic anaemia, where the body does not make enough new blood cells.
FSA chief executive Catherine Brown accused some vets and horse owners of not ensuring horse passports are kept up-to-date, leading to bute-treated horses ending up in the food chain.
Responding earlier to an urgent question in the House of Commons, food minister David Heath said that retailers and suppliers were "on course" to provide "meaningful results" on testing of beef products on Friday.
He confirmed that tests on Findus products had revealed no trace of bute. Findus withdrew its beef lasagne from sale after tests found it to contain up to 100% horsemeat.
Shadow environment secretary Mary Creagh - who tabled the Commons question - went on to accuse the government of complacency over the danger of bute entering the human food chain.
She first raised concerns in the House about bute contamination in January.
Meanwhile, Aintree Racecourse has confirmed reports that the Peter Boddy Licensed Slaughterhouse in Todmorden, West Yorkshire, under investigation in the horsemeat inquiry, has the contract to remove dead Grand National racehorses for disposal purposes.
But it said it was illegal for horses humanely put down by injection on the racecourse to be sold for consumption and was "as confident as we possibly can be that no unfit meat ever reaches the human food chain".