France has pinned much of the blame for Europe's horse scandal on a French firm that allegedly sold 750 tonnes of horsemeat as beef that ended up in millions of ready-to-eat meals sold across the continent.

The move came Thursday as police in Britain arrested three men suspected of passing horse off as beef, and as Germany joined the ranks of countries where frozen "beef" lasagne was found to contain horsemeat.

The Dutch government's food and consumer watchdog has also searched and carried out tests for horsemeat at around 100 businesses, as Europe's tainted beef scandal deepens.

In a sign of the damage the scandal has done to consumer confidence, 11 major food retailers and suppliers issued a public letter in Britain on Friday saying they shared people's "anger and outrage" and were "working around the clock" to identify what has gone wrong.

Evidence of horsemeat has until now been confined to frozen products, but Asda supermarket in Britain announced Thursday it had pulled a fresh beef bolognese sauce from the shelves after tests revealed it contained horse DNA.

The scandal has left governments scrambling to figure out how the mislabelling of the meat started in the sprawling chain of production spanning abattoirs and meat suppliers in countries across Europe.

The French government threw some light on that question when it presented the results of an investigation that pinned much of the blame on Spanghero, a meat-processing firm in the southwestern town of Castelnaudary.

The findings by the DGCCRF anti-fraud office, presented by Consumer Affairs Minister Benoit Hamon, are staggering.

It said Spanghero had knowingly sold 750 tonnes of horsemeat mis-labelled as beef over a period of six months, 500 tonnes of which were sent to French firm Comigel, which makes frozen meals at its Tavola factory in Luxembourg.

That meat was used to make 4.5 million products that were sold by Comigel to 28 different companies in 13 European countries, it said.

Hamon said Spanghero would be prosecuted and officials said its licence to handle meat would be suspended pending further investigations.

The minister told reporters that Comigel, which supplied millions of ready-to-eat meals to supermarkets across Europe which have now removed them from their shelves, had been deceived by Spanghero.

But he said that Comigel had failed to carry out tests or properly inspect paperwork that would have alerted it to the scam. He added that Romanian abattoirs named in the affair appeared to have acted in good faith.

Spanghero on Thursday again denied any wrongdoing, saying in a statement that it had never ordered, received or resold any meat that it did not believe to be beef.

In Britain, where unlike continental European countries eating horse is taboo, police said three men suspected of passing horsemeat off as beef were arrested Thursday on suspicion of fraud.

Two were arrested in Aberystwyth in Wales where a food processing plant is based, and one was detained in northern England, where police raided a slaughterhouse on Tuesday.

Both the processing plant and the slaughterhouse were shut down by Britain's Food Standards Agency on Wednesday. They are the first plants in Britain accused of selling horsemeat labelled as beef.

Concerns about horsemeat first emerged in mid-January when Irish authorities found traces of horse in beefburgers made by firms in Ireland and Britain and sold in supermarket chains including Tesco and Aldi.

The scandal spiralled last week when Comigel alerted Findus to the presence of horsemeat in the meals it had made for the food giant and which were on sale in Britain.

Since then retailers in Britain, Sweden, France, Switzerland, Germany and the Netherlands have removed Comigel products such as meatballs, hamburgers, minced meat and lasagne.

Two supermarket chains in Germany, Real and Edeka, said Thursday that they had found traces of horsemeat in frozen lasagne that they had pulled as a precautionary measure off their shelves last week.

After emergency talks in Brussels on Wednesday, the EU's health commissioner Tonio Borg said the block was calling on all of its 27 member states to carry out DNA tests on beef products.

France's Agriculture Minister Stephane Le Foll meanwhile said authorities had located and would destroy three horse carcasses that tested positive for an equine drug that is potentially harmful to humans.

He said that the carcasses, which had arrived in France from Britain, were "another affair" that had nothing to do with the wider horsemeat scandal.