Environment Secretary Owen Paterson promised to “take the necessary action" if any health risks are discovered in contaminated meat, adding there may more bad news to come.
Whilst no danger has been found in humans eating horse meat, the Food Standards Agency have confirmed that tests have been ordered on products for the veterinary drug phenylbutazone, as animals treated with "bute" are not allowed to enter the food chain.
Frozen foods firm Findus, which has taken its beef lasagne's off shelves after some were found to have up to 100per cent horse meat in them, said it was looking into legal action as an internal investigation "strongly suggests" that the contamination "was not accidental".
The food supplier said it carried out a full product recall on Monday, two days before DNA tests found that some of its lasagnes contained up to 100 per cent horse meat.
Supermarkets Tesco and Aldi have also withdrawn a range of ready meals produced by Comigel over fears that they contained contaminated meat.
The government has warned that more cases of contaminated meat may surface within days, as the next set of results could reveal further traces of horse meat.