The man fell about 20 feet (six meters) to his death apparently while trying to slide down a railing of a staircase on a bridge, according to the prosecutor's office in the western city of Nantes.
Police and the prefecture said the man, not identified, was 21, not 23 as reported by the prosecutor's office. He died at the Nantes hospital hours after his fall at around 3 a.m. (0100 GMT, 9 p.m. EDT Wednesday).
The party that began Wednesday night in Nantes' city center was held at the same time as a giant party in Montpellier, in southern France, which drew an estimated 10,000 revelers.
Nantes' regional prefect Jean Daubigny told 1Tele TV station that 57 revelers were hospitalized after drinking too much. Police said 41 people were jailed. There were no fatal incidents at the Montpellier event.
"Regrettably, we saw some people who had totally lost control of themselves," Daubigny said. Among those treated by rescue workers were adolescents aged 14 and 15, he said.
Because such events are organized anonymously on the social network Facebook, authorities cannot work with organizers to ensure safety, he said.
In fact, the Nantes prefecture got wind of the gathering and forbid the sale and transport of alcohol in the city center Wednesday night. In France, large public gatherings need prior authorization to take place.
Scenes of the party in Montpellier were shown on YouTube.
But Paris police are already bracing for a giant cocktail party planned for May 23. Police headquarters posted its own Facebook note, warning that the event to be held at the Champ de Mars, a grassy esplanade near the Eiffel Tower is illegal -- as is drinking alcohol there.
It noted that 14 people were hospitalized after a similar event recently in the Breton city of Rennes.
"Without denying the festive and convivial motive ... of the planned May 23 event, police want to note the grave risks linked to crowd control of several thousand people," the post says before getting to the point: "consuming alcohol is strictly forbidden on the Champ de Mars" and those organizing such a large gathering without a permit risk a six-month prison sentence and a euro7,500 fine ($9,450).
