Tesco has vowed to DNA test its meat after the horsemeat scandal, saying the rogue burgers from supplier Silvercrest, "did not come from the list of approved suppliers".
The supermarket chain has dropped the frozen burger supplier following what it termed a "breach of trust".
In a statement released on Wednesday the supermarket chain said the meat was not from the UK or Ireland either, "despite our instruction that only beef from the UK and Ireland should be used in our frozen beef burgers."
It has vowed to introduce a DNA testing system on meat products to "ensure the quality" of the food on its shelves in the wake of the scandal.
It said: "We now understand - with as much certainty as possible - what happened.
"The evidence tells us that our frozen burger supplier, Silvercrest, used meat in our products that did not come from the list of approved suppliers we gave them.
"Nor was the meat from the UK or Ireland, despite our instruction that only beef from the UK and Ireland should be used in our frozen beefburgers.
"Consequently we have decided not to take products from that supplier in future. We took that decision with regret but the breach of trust is simply too great."