"We can't say for the moment what the quantity is," a Coop spokeswoman told AFP.
Earlier Wednesday, the Coop group published a statement on its website saying it had turned to independent testers amid concerns that products labelled as beef could contain horsemeat.
"External testing revealed the presence of horsemeat in Coop's Lasagne Verdi brand," it said, adding that customers who returned the affected product would receive a full refund.
On Tuesday Coop, which has stores only in Switzerland, had announced that it was withdrawing all Comigel-produced lasagne as a precautionary measure.
British supermarkets were the first to pull the products last week after Comigel warned that the products it supplied to the Findus frozen food giant — which sold its ready-to-eat meals to supermarkets — was suspect.
Comigel said it got its meat from another French firm, Spanghero, which said it was supplied from two abattoirs in Romania who allegedly passed horsemeat off as beef.
Comigel sells its products to customers in 16 countries.
Frozen meals made by Findus have remained on Coop's shelves, however.
Findus Switzerland, which unlike the rest of the brand still belongs to Nestlé, only uses Swiss beef in its lasagnas, Nestle said at the weekend.
Nestlé owned all of Findus until 2000 when it sold the rights to most of the brand to a Swedish private equity firm. The Findus brand, excluding in Switzerland and Italy, is today owned by British private equity firm Lion Capital.
Eating horsemeat is relatively common in Switzerland — unlike in Britain, where it is a taboo — meaning concerns here have focussed on alleged labelling fraud.