Investigations are under way to try to discover how horsemeat got into some beef burgers on sale in UK and Irish supermarkets.
The burgers have been removed from stores and food safety officials say there's no human health risk.
The contaminated burgers had been stocked by a number of supermarkets, including Tesco and Iceland.
The burgers from Tesco were tested and almost 30% of one sample contained horsemeat.
It wasn't just horsemeat that was found. Pig DNA was also discovered in some beef meal products as well.
Tesco has apologised to its customers and say they're "working... to ensure it does not happen again".