21 people arrested in south of France over claims horses used in medical research were illegally sold for human consumption

French police carried out dozens of early-morning raids on Monday after reports that horses used for medical research were illegally sold for human consumption.

Investigators said 21 people including veterinarians, butchers and other meat industry workers had been arrested in what they described as a vast operation across the south of France.

The animals were bought from a research laboratory belonging to the French pharmaceutical giant Sanofi and were supposed to have been destroyed, but instead they were allegedly issued with false papers and sold to abattoirs between 2010 and 2012.

The raids come 10 months after a French company was found to be putting horsemeat into ready-made dishes labelled as having been made with beef, causing an Europe-wide scandal.

Sanofi said it had used the horses to incubate antibodies to manufacture purified serums used against rabies, snake bites and tetanus. The company said the animals were in good health but certified as not fit for human consumption.

Alain Bernal, of the Sanofi Pasteur vaccine division, said the company was co-operating with investigators but had no idea how long the fraud had been going on. He said the company had disposed of around 200 horses in the last three years. The animals are sold for a "symbolic amount" and issued with identification papers clearly stating "not to be killed for human consumption".

In September eight managers from the French firm Spanghero at the centre of the earlier scandal, which erupted in February, were formally put under investigation for fraud. The company, which employed 360 staff, closed in June, but reopened under new management two months later.

British and Irish supermarkets among many others across the EU were found to have sold the company's ready-made meals.

Monday's raids took place in 11 French departments across southern France including Provence and the Côte d'Azur. The local television station France 2 Languedoc Roussillon claimed that other animals treated with anti-inflammatory drugs or antibiotics, making them unfit for human consumption, had also been acquired from equestrian centres and even individual horse owners and had fraudulently entered the food chain through the same network.

The French consumer minister, Benoït Hamon, told RTL radio the two scandals were unrelated. "They were selling horsemeat in place of beef, which is commercial fraud. Here we could be talking about a health problem, which is different," he said.

However, his government colleague Guillaume Garot, the junior agriculture minister, said: "At this stage, there is nothing to suggest a health problem. That's exactly what's being investigated."