Horses which have been treated with phenylbutazone or 'bute' are not allowed to enter the food chain. The FSA carries out checks in slaughterhouses to ensure that horses presented for slaughter are fit for human consumption, in the same was as they do for sheep and cattle, etc.
The FSA also carries out regular enhanced sampling and testing for phenylbutazone in meat from horses slaughtered in the UK.
In 2012 the FSA identified five cases where horses returned non-compliant results. None of the meat had been placed for sale on the UK market. Where the meat had been exported to other countries, the relevant food safety authorities were informed.
During the recent horse meat incident the Food Safety Authority of Ireland (FSAI) checked for the presence of phenylbutazone and the samples came back negative.
More top news
David Cameron is expected to announce a new plan that will see Britain take in thousands more Syrian refugees.
Reports Ed Miliband is to rule out a return to frontline politics have been described as "speculation" by sources close to the politician.
Designer brand Hugo Boss faces a hefty fine for health and safety breaches after a boy was crushed to death by an 18-stone mirror