More than 2,500 partygoers attended the illegal party in the region of Brittany in France, despite the government's strict coronavirus restrictions and a national night-time curfew.
About 1,600 fines were issued as of Saturday following the rave, which started on Thursday, French Interior Minister Gerald Darmanin said via his official Twitter profile.
Trucks, sound systems and generators have been seized and Gendarmes officers "are continuing their investigation and checks so that this illegal event is harshly sanctioned," Darmanin added.
Of the 1,200 fines, 800 are related to coronavirus restrictions, Emmanuel Berthier, prefect of Ille-et-Vilaine, said.
Up to 20 vehicles including trucks which may be carrying sound equipment managed to escape the police block, Sauvegrain added.
"There is a judicial investigation which will allow us to identify the main perpetrators and to arrest them," Sauvegrain added.
Local police said they had tried to shut down the rave, but "faced violent hostility," with a police vehicle set on fire, other vehicles damaged, and soldiers sprayed with bottles and stones, causing minor injuries.
"No new violence" occurred since Thursday, a Gendarmerie Nationale spokesperson told CNN on Saturday, adding that partygoers were "leaving the premises voluntarily."
Local authorities said the number of partygoers was "estimated at 2,500, coming from different French departments and from abroad."
A national curfew from 8 p.m. to 6 a.m. has been in place since December 15.