Picard, a retailer which has hundreds of outlets across France, said tests had confirmed that horsemeat was present in two lots of frozen "beef" lasagne meals it removed from its shelves last week after the scandal broke.
It said the products were made by Comigel, the French firm at the heart of the food scare spreading across Europe, and said it was now waiting for results of a probe by French officials to determine "at what level the fraud is situated".
Picard was one of several major French retailers that last week pulled products made by Comigel, which produced the Findus lasagne that was found by Britain to contain up to 100 percent horsemeat.
Retailers in Britain, Sweden, France, Switzerland and the Netherlands have been removing Comigel products such as meatballs, hamburgers, minced meat and lasagne after the firm alerted Findus to the presence of horsemeat in its meals.
Health officials have been testing frozen food products in these countries but so far only Britain and France have found cases of wrongly labelled meat.
Comigel denies any wrongdoing and has said it got its meat from another French firm, Spanghero, which said it was supplied from two abattoirs in Romania who allegedly passed off horsemeat as beef.
But Romanian Prime Minister Victor Ponta on Tuesday angrily denied his country was to blame.
He said Spanghero did not have a direct contract with Romanian firms and that checks carried out since last week had shown that there had been no violation of European rules and standards by the abattoirs.
Ireland's agriculture minister has called a meeting in Brussels on Wednesday with the EU's health commissioner Tonio Borg and other top officials to discuss action needed at the EU level to resolve the issue.
The results of a French inquiry into the scandal were due to be made public by Thursday.