According to local media reports, Steve Maia Carriço, a 24-year-old from a Portuguese family resident in France, had been missing since 22 June, and was last seen during a police operation at a party he attended in Nantes.

Carriço was attending a techno music festival, part of a traditional festival that took place in towns and cities around France, with thousands of people attending. In Nantes, where the event degenerated into disturbances, police intervened and several people fell into the river.

The body was taken out of the Loire at Nantes on Monday night and, according to rolling news channel BFMTV, which cited several different sources, an autopsy confirmed that it was Carriço.

The authorities have announced the opening of an investigation into suspected "involuntary homicide", while several other efforts are underway to try to clarify the circumstances of the police operation.

Carriço’s disappearance caused shock waves in France, because of the images and descriptions of the police intervention, in which tear gas and rubber bullets were used against young people.

There are reports that 14 youngsters fell into the river and had to be rescued by the firefighters, but friends and family never heard from Carriço again.

The operation is being investigated by the national police inspectorate, and a separate process is underway to ascertain the causes of Carriço’s disappearance.

Two French associations are suing the authorities on behalf of more than 80 people who were present at the time of the police charge. It alleges that the police action "endangered the lives" of young people with "deliberate violence", and includes testimony from some 140 witnesses.

According to a report by the France 3 channel of Nantes, Carriço could not swim.