Environment Secretary Owen Paterson has told Sky News an "international conspiracy" could be at the centre of the horsemeat scandal, as he warned that further cases of contaminated meat may be revealed within days.
Mr Paterson said the next set of results on all retailers' and manufacturers' processed beef products could show more traces of horsemeat.
"There may well be more bad results coming through, that's the point of doing this random analysis," Mr Paterson said.
The results, ordered by the Food Standards Agency, are due on Friday.
Mr Paterson held an emergency meeting with food producers, leading supermarkets and the Food Standards Agency (FSA) in central London on Saturday.
He said it had been agreed that there would be "a very rapid analysis of current products", with results by the end of next week, to understand "the extent of this problem which is either caused by gross incompetence or what I suspect is actually an international criminal conspiracy".
"If there's a criminal act we will work with the authorities wherever they are to ensure the appropriate measures are taken," he said.
The talks came as frozen food company Findus UK said it is considering legal action against its suppliers after tests found up to 100% horsemeat in some of its beef lasagnes.
"Findus is taking legal advice about the grounds for pursuing a case against its suppliers, regarding what they believe is their suppliers' failure to meet contractual obligations about product integrity," the statement said.
"The early results from Findus UK's internal investigation strongly suggests that the horsemeat contamination in Beef Lasagne was not accidental."
Enterprising eBay users have already taken to auctioning the firm's beef lasgnes, with one receiving bids of £12 - with proceeds apparently going towards Help The Heroes charity.
Mr Paterson also warned that the scandal "could go deeper than we thought".
Substituting horse for beef was "fraud on the British public" and "people should buy what is on the label," he said.
The Environment Secretary said that retailers held the "ultimate responsibility" for making sure that horsemeat was not in their products and that they would have to start doing their own testing.
Scotland Yard met with representatives from the FSA on Friday night over the scandal.
During the talks on Saturday morning the supermarkets had agreed to work with the FSA to report their test results on a quarterly basis.
Bosses from leading supermarkets including Tesco (Other OTC: TSCDY - news) , Sainsbury (LSE: SBRY.L - news) 's, Asda and Morrisons attended the meeting at the Department for Environment, Food and Rural Affairs (Defra).
Findus was not invited to the Government summit but the Food and Drink Federation, of which they are a member, attended.
Earlier, Findus reiterated its apology for the scandal, but it came under fire from opposition leader Ed Miliband amid reports the company knew some days before it withdrew its lasagnes from sale that they were likely to contain horsemeat.
Mr Miliband told Sky News: "The head of the company needs to come to Britain and explain himself and who knew what when.
"Many customers were innocently buying Findus products when it appears that the company may have known it was likely to be contaminated by horsemeat."
Findus has strongly denied other reports saying it knew about the problems as early as last August, saying that they first suspected an issue on January 22, when they ordered the initial tests.
The presence of equine DNA was confirmed on January 29 and a product recall was ordered on February 2 after further tests had been conducted.
Aldi meanwhile has confirmed that two of its ready meal ranges produced by Comigel, the French supplier also used by Findus, were found to contain between 30% and 100% horsemeat.
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