The month-old horsemeat scandal in Europe expanded this week as authorities claim phenylbutazone was found in eight horse carcasses, and that six of those carcasses may have entered the food chain. Phenylbutazone, commonly referred to as bute, is banned from products entering the food system due to potential serious complications for humans.

England’s chief medical officer, however, said Thursday the highest level of bute detected was 1.9mg of bute per kg of horsemeat, which posed “very little risk to human health.”

The European horsemeat scandal was discovered January 15 when tests by Irish authorities found horsemeat in beef burgers made by firms in the Irish Republic and the UK and sold in supermarket chains. The UK’s Environment Secretary Owen Paterson told the House of Parliament that the mixing of horsemeat with beef was a case of food fraud, but that there was no evidence of a food safety issue.

Phenylbutazone is a non-steroidal anti-inflammatory drug for the short-term treatment of pain and fever in animals. In horses, bute is often used for pain relief from infections, sprains, tendinitis, arthritis and laminitis. Phenylbutazone was originally made available for use in humans for the treatment of rheumatoid arthritis and gout in 1949. However, it is no longer approved, and therefore not marketed, for any human use in the United States. In rare cases bute can cause a serious blood disorder known as aplastic anaemia, where the body does not make enough new blood cells.

Although bute is not allowed in the food chain, a BBC News report suggests that horses given bute do enter the food system on a regular basis. BBC reporter James Gallagher wrote that one estimate “suggests 540 bute-treated horses leave the UK shores each year, destined for dinner plates on Continental Europe.”

Still, authorities are attempting to down-play the danger to humans. Chief medical officer Prof. Dame Sally Davies said an individual would need to consume vast quantities of bute-contaminated horsemeat to be at risk.

“A person would have to eat 500 to 600, 100 percent horsemeat burgers a day to get close to consuming a human’s daily dose. [The drug] passes though the system fairly quickly, so it is unlikely to build up in our bodies,” she said.

The source of the food fraud cases remains under investigation, but the UK’s Paterson said, “It is already clear that we are dealing with Europe-wide supply networks. I am taking action to ensure that there is effective liaison with the European Commission and other member states.”

At a meeting Wednesday in Brussels, officials proposed a three-month program of control measures throughout the EU, including random testing of processed beef products and testing for horsemeat residue in slaughterhouses.