Phenylbutazone is an anti-inflammatory treatment for horses which is potentially harmful to humans and is banned for consumption. London alerted Paris that six tainted carcasses had been exported from Britain to France in January, but by that time the contaminated meat had already been processed.

Agriculture Minister Stephane Le Foll said that although some of the meat had been recalled, the equivalent of three carcasses had "probably" made it to consumers.

There was however "no health risk" since the traces of phenylbutazone found in the meat were "extremely weak", he said. This incident was not connected with the wider horsemeat scandal since the meat had not been disguised as beef, he said.

But the announcement nevertheless added a new dimension to the scandal.

The row over mislabelled meat erupted in Europe last month after horsemeat was initially found in so-called beef ready-made meals and burgers in Britain and Ireland.

Since then, supermarkets across the continent have pulled prepared meals from their shelves, with effects felt as far away as Hong Kong where an imported brand of lasagne has been withdrawn from stores.

On Saturday, Italy joined the long list of countries that have been hit by the fraud, reporting its first case of horsemeat-contaminated lasagne.

Horsemeat was found in tests on six tonnes of mincemeat and 2,400 "lasagne bolognese" packages produced by a central Italian firm that had used meat from suppliers based in the northern part of Italy.

The tests were carried out as part of checks by police on 121 brands across the country.

French firm Spanghero has been at the heart of the scandal after it allegedly passed off 750 tonnes of horsemeat as beef. The product eventually found its way into 4.5 million "beef" products sold across Europe.

In Ireland, authorities on Friday suspended production at a meat processing plant after investigators found it was selling horsemeat labelled as beef.

B&F Meats was found to be sending horsemeat to a customer in the Czech Republic.