Asda is recalling all corned beef from its budget range after traces of the veterinary drug phenylbutazone were found in some batches in the UK.
Britain’s Food Standards Agency said "very low levels" of the painkilling medicine, known as bute, were detected in the Asda Smart Price Corned Beef.
Customers who have bought the 340g tins, with any date code, have been urged not to eat the corned beef and to return it to the supermarket.
Asda withdrew the product on 8 March after it was found to contain more than 1% horse DNA.
Bute was detected in some samples, at the level of four parts per billion (4ppb), when further tests were carried out.
The corned beef is the only meat product in which bute has been found, according to the FSA.
Bute had been discovered in horse carcasses in February however, with the highest level found being 1900ppb.
The FSA said no other Asda products are thought to be affected and that customers who bought the corned beef should contact the supermarket for a refund.
They said that while animals treated with bute should not enter the food chain, the risk of damage to the health of anyone who had eaten such meat is "very low".
Chief Medical Officer Professor Dame Sally Davies previously said: "Horse meat containing phenylbutazone presents a very low risk to human health.
"Phenylbutazone is a commonly used medicine in horses. It is also prescribed to some patients who are suffering from a severe form of arthritis."
Horse carcasses in the UK need to have a negative bute test before they can enter the food chain.
In a statement on the Asda website, the supermarket said it was also recalling tins of Chosen By You corned beef.
"The tinned Chosen By You Corned Beef (340g) product, also withdrawn in March, has not tested positive for phenylbutazone," the company said.
"However, as a precaution, it is also being recalled as it is made in the same factory."
Asda claimed to have taken "an extremely cautious approach since the very beginning" and had carried out more than 700 tests so far, "moving swiftly to remove any products" when it had any concerns.
The supermarket added: "The FSA has reassured us that the quantities we've found pose a low risk to human health."