Some 25 people, including wholesalers, vets, dealers and butchers, stood trial in Marseille on Monday over the alleged scam that saw fake documentation given to horses previously used to produce serums by French pharmaceutical company Sanofi-Pasteur at a laboratory farm in southern France.

They had reportedly received jabs against rabies, tetanus and venoms.

After an anonymous tipoff in 2012, investigators found cysts and ganglions on necks, as well as an “S” for Sanofi on the rump of former racing horses which should have been retired after being released by the company but that ended up on the butcher’s block.

Eight vets are among the defendants, accused of failing to spot telltale signs the horses had been used for pharmaceutical tests.

Despite being clearly marked as “permanently barred from slaughter for human consumption”, the animals were given new paperwork declaring them edible and were butchered in Narbonne in southern France, Verona in Italy and Barcelona in Spain.

While the horses’ treatment was illegal, an expert tasked with assessing the dangers of eating their meat concluded that there was “no major toxicological risk” for consumers.