The complainants are two young men and four young girls, aged 17 to 18, who were at the International University Music Festival (FIMU), Belfort public prosecutor Jessica Vonderscher told AFP.

“We have signs of bites, as we have seen on other festivals or other evenings,” she explained, confirming information from the regional daily L’Est Républicain.

Only “three people went through the hospital emergency room” overnight from Saturday to Sunday for tests to determine if a product had been injected into them and, if so, what type of substance”, said continued Ms. Vonderscher, who did not yet have the results of these analyses.

The other three people were also referred to the hospital for tests but did not go there for the moment, added the magistrate. “The interest is that they go there,” she insisted.

An investigation has been entrusted to the Belfort police, according to Ms. Vonderscher.

An unexplained wave of stings has affected nightclubs, bars and festivals across France in recent months, with complaints lodged from Lille to Béziers (Hérault) and from Lorient (Morbihan) to Strasbourg, via Grenoble, Nancy, Lyon, Besançon, Valence.