Twenty-nine beef products out of 2,501 tested in Britain have been found to contain more than one percent horsemeat, the Food Standards Agency said on Friday.
FSA chief executive Catherine Brown said: "The overwhelming majority of beef products in this country do not contain horse. The examples we have had are totally unacceptable, but they are the exceptions."
All of the 29 products containing horsemeat have already been withdrawn from sale, she added.
These include lasagne and spaghetti bolognese sold by Aldi supermarkets, burgers sold by Co-op stores, and burgers and spaghetti bolognese sold by Britain's leading supermarket chain Tesco.
Beef lasagne made by the frozen foods giant Findus, as well as burgers for the catering industry produced by Irish firm Rangeland, were also on the list.
Brown stressed that the results were "still far from the full picture" and that testing continued on other products.
Pub and hotel group Whitbread on Friday became the latest company in Britain to admit horse DNA had been found in its food, saying two of its products -- meat lasagnes and beefburgers -- had been affected.