Tesco and Aldi issued statements saying they are boosting testing on meat products to protect customers, restore confidence and ensure product quality.

Jim Smith, group technical director for Tesco, said the company will "no longer work with the suppliers who fell below our very high standards."

The Food Standards Agency declined to give details of the names or location of the three food premises raided Friday.

Investigations are ongoing, but authorities cannot rule out the possibility of arrests, it said.

Authorities across Europe have been scrambling to get a grip on the crisis over rogue horse meat in beef products.

The European Union intends to begin testing meat across all 27 member states, it confirmed Friday.

It called for testing 10 to 150 samples per country and at least five tests per country for the presence of the drug phenylbutazone, also known as bute, which is approved for horses but is not allowed to enter the food chain because it can be harmful to humans.

Unauthorized horse meat has been discovered in a variety of products labeled as beef that were sold in supermarkets in countries including Britain, France, Sweden, Switzerland, Germany and Ireland.

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 in beef products 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.