Preliminary tests on beef products for traces of other meats have found seven samples may contain horse DNA above 1%, the Food Standards Agency (FSA) has said.
Further tests will now be carried out on the samples, which come from six different products.
The checks also found three products that contain levels of pig DNA above 1%.
These have already been listed on the companies' websites and are Asda's spaghetti and meatballs, its beef cannelloni and Apetito beef lasagne, the agency said.
Both Asda products have been withdrawn from sale while Apetito has indicated that almost all of its product will have been served although unused stock can be returned.
The test results represent the first and second phase of testing by the FSA with samples taken from a wide range of businesses including shops, wholesale and catering suppliers to schools and hospitals.
The agency said in a statement: "For phase one, two products contain levels of pig DNA above 1%. So far, no products are verified as containing horse DNA at a level above 1%. Preliminary tests show that seven samples, representing six different products, may contain horse DNA above 1% and a further three may contain pig DNA above 1%. However, further checks are needed to verify this. Where levels over the 1% threshold are confirmed, the FSA will publish details as soon as this information is received. For phase two, one product tested to date contains levels of pig DNA above 1%; none contain horse DNA above this level. Full results of phase two are awaited."
Many of the UK's biggest food firms and supermarkets have recalled beef products after tests found they contained horse DNA.
The first phase of testing saw 224 samples of minced beef products including burgers, minced beef, beef sausage or meatballs checked for horse and pig DNA, while the second involves 140 samples of beef-based ready meals including frozen, chilled or canned lasagne, chilli con carne, cottage pie, ravioli, cannelloni and spaghetti bolognese being tested for horse and pig DNA. A third phase of testing is seeing a further 150 samples examined for traces of horse DNA. Full details of the sampling programme are to be published in a report by the FSA next month.
The agency also said that it has lifted its suspension of the Peter Boddy slaughterhouse in Todmorden, West Yorkshire, after it was raided as part of the investigation on February 12.