Beef products sold by Birds Eye, Taco Bell and catering supplier Brakes have been found to contain horse DNA in the latest round of tests carried out since the start of the meat scandal, the Food Standards Agency has confirmed.
The third round of tests carried out since January revealed contamination of Birds Eye Traditional Spaghetti Bolognese and Beef Lasagne, Taco Bell's ground beef and Brakes' spicy minced beef skewer, the FSA said.
Ten tests on the four products returned results of more than 1% horsemeat, the agency said, and all four have been withdrawn from sale.
Birds Eye had previously withdrawn three beef ready meals from supermarkets in the UK and Ireland as a precaution after horse DNA was found in a product in Belgium. The company said its chilli con carne had tested positive for 2% horse DNA.
Taco Bell's three London stores closed in the mid-1990s. Only one public Taco Bell is still running in the UK, at the Lakeside Shopping Centre in Essex. Two others operate on US Air Force bases in the UK.
US-owned Tex-Mex restaurant chain Taco Bell said that it was "disappointed" to have discovered the horse meat in tests it carried out on beef supplied to its UK restaurants by a sole European supplier.
"We immediately withdrew ground beef from sale in our restaurants, discontinued purchase of that meat, and contacted the Food Standards Agency with this information," it said in a statement.
"We would like to apologise to all of our customers, and we can reassure you that we are working hard to ensure that every precaution is being undertaken to guarantee that we are only supplied with products that meet the high standards we demand."
Birds Eye had already withdrawn the spaghetti bolognese, lasagne and a third ready meal, a shepherd's pie, from sale in Britain and the Republic of Ireland as a precaution after tests found 2% of horse DNA in a chilli con carne dish it sold in Belgium.
They are made by the same Belgian manufacturer, Frigilunch NV.
"No other Birds Eye products have tested positive for horse DNA, nor do they share the same supply chains as Frigilunch NV," the company said in a statement.
"Going forward we are introducing a new ongoing DNA testing programme that will ensure no minced beef meat product can leave our facilities without first having been cleared by DNA testing."
Brakes, which is based in Ashford, Kent, is the supplier for the House of Commons Catering Service and last month it withdrew its steak and kidney pie, beef and onion pie, steak and kidney suet pudding, and beef Italian meatballs as a precaution.
It also supplies pubs among 19,000 customers who buy around 48,000 cases of products containing beef every week.
It too said it was introducing new tests after the discovery, alongside 259 negative tests.
"Our testing programme represents a significant proportion of all results the FSA has obtained from across the food industry," it said.
"Our tests also confirmed one positive equine DNA finding at between 1% and 10% on a Brakes spicy minced beef skewer and one positive test reported by a customer of our subsidiary division Creative Foods, on a lasagne manufactured exclusively for them.
"Brakes have also segregated a frozen burger as a precaution after equine DNA at 1% was reported to the Food Standards Agency.
"Brakes and Creative Foods are very disappointed to have been let down by our respective suppliers and have sincerely apologised to our customers.
"As any responsible company, we have a duty of care to all our customers and the consumers they serve to guarantee the integrity of the products we purchase."
A first wave of tests carried out since the scandal broke found horse meat in products including Aldi's special frozen beef lasagne and special frozen spaghetti bolognese, Co-op frozen quarter-pounder burgers, Findus beef lasagne, Rangeland's catering burger products, and Tesco Value frozen burgers and Value spaghetti bolognese.
A second wave of tests revealed contamination of Asda's chilled beef bolognese sauce, beefburgers, minced beef and halal minced beef sold by Sodexo, which supplies food to schools, care homes and the armed forces, and a Whitbread Group lasagne and beefburger.
McDonald's has confirmed tests for horse meat in its products came back negative.
Jill McDonald, the president and chief executive of McDonald's UK, said: "We voluntarily provided samples of all beef burgers currently available on our menu to the Food Standards Agency (FSA) for their own tests.
"All tests, including our own, have now been completed and we can confirm that no horse meat has been found in any of McDonald's products.
"Our beef supply chain is short and transparent and has just five simple steps from the farms through to the food we serve in our restaurants. Thanks to this our customers can continue to trust in the quality of food at McDonald's."
Sales of frozen hamburgers from major retailers have plummeted after the horse meat scandal that has deeply shaken public confidence in processed meat in Europe, a consumer research firm said.
From January 17 to February 17, sales of frozen hamburgers fell by a full 43 percent in the United Kingdom, according to the London-based group Kantar Worldpanel, which gathers consumer data from about 30,000 households throughout the UK.