Findus UK said Saturday it was taking legal advice after early results from its internal investigation "strongly suggest" that the presence of horsemeat in its frozen beef lasagne meals was "not accidental".
They have also been told by their French frozen food supplier Comigel that "the contamination" of processed beef products with equine flesh could date back to August 2012.
"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," it said in a statement.
"The early results from Findus UK's internal investigation strongly suggest that the horsemeat contamination in beef lasagne was not accidental."
In an earlier statement, Findus said they wanted to be "absolutely explicit that they were not aware of any issue of contamination with horsemeat last year.
"They were only made aware of a possible August 2012 date through a letter dated 2 February 2013 from the supplier Comigel.
"By then Findus was already conducting a full supply chain traceability review and had pro-actively initiated DNA testing."
The opposition Labour lawmaker Tom Watson earlier claimed he had been shown by a retailer a copy of a letter that Findus sent to them on Monday.
He published an extract on his website.
"Investigations have led one of our suppliers based in France to inform us in writing on 2nd February 2013 that the raw materials delivered since 1st August 2012 are likely to be non-conform and consequently the labelling on finished products is incorrect," it said.
Britain's Food Standards Agency regulator announced Thursday that 11 of 18 samples of Findus beef lasagne were found to contain between 60 and 100 percent horsemeat.
Asked by AFP to comment on Britain's food minister fearing a criminal conspiracy, a Findus spokesman said: "That's part of our investigations. We need to understand how the meat got into the supply chain. That's something we are working on with Comigel, as the supplier."
He did not know how long the investigation would take.
The spokesman said it was "still uncertain... where the meat exactly came from".
"The supplier has asked us to withdraw the raw material batches."
Findus said it was not taking part in the emergency food industry meeting which took place Saturday at the Department for Environment, Food and Rural Affairs.
"Findus did not receive an invitation to this summit. However they are aware that the Food and Drink Federation, of which they are a member, will be attending," they said.
Findus has withdrawn various frozen meals from the market in France and Sweden.