Supermarkets across the UK have withdrawn batches of lamb distributed by an Anglesey company because of a health scare.
Some lamb and offal was recalled from Asda
Asda and wholesaler Makro have both been affected by the recall.
According to the Food Standards Agency, the meat might contain traces of drugs and should not have entered the human food chain.
The meat was distributed by Welsh County Foods based in Anglesey. A vet there smelt sheep dip on carcasses.
Some of the sheep had been treated with drugs to combat sheep scab, but it is reported that the drugs were not given enough time to pass through the animals' systems.
The FSA is investigating how the breeding sheep were slaughtered early.
Repeated exposure to one of the drugs - Doramectin - has caused sickness and other effects in laboratory animals, but a spokeswoman for FSA said effects on human were unknown.
Asda said the likelihood of people eating contaminated meat was "low" but had issued a recall notice as a precautionary measure.
The FSA issued a "food alert" and shops withdrew the batches from shelves from Friday, but it was unclear how much lamb was involved.
The FSA also said it was unsure where in the UK the lamb was being sold, and its investigation was continuing.
Welsh Country Foods managing director Trevor Hanger said: "We have been fully co-operating with the Food Standards Agency over this matter.
"We are confident that our traceability records have identified all the likely destinations for this lamb. Following guidance from the FSA we have contacted all of our potentially affected customers and have instructed them to withdraw these products from sale."