CORNUSSE, France (AFP) — Up to 40,000 partygoers gathered on Saturday for an illegal rave at a military site in France, defying warnings about the risk of possible explosions from old ordinance.

Thumping techno music echoed across a vast firing range near the central French town of Bourges as revellers — many dressed in brightly colored outfits, others shirtless — assembled for the unauthorized event, known as a “free party,” which began on Friday.

Behind them, tents and vans stretched across the grassy field.

Authorities had estimated attendance at 20,000 on Saturday morning, but more ravers arrived during the day and Tekno Anti Rep, a free party support network present at the site, told Agence France-Presse (AFP) the total was between 35,000 and 40,000 by the evening.

Bomb disposal experts had to intervene after a shell was discovered near a road passsing through the party site, the local officials said.

The gathering comes as the French parliament is seeking to tighten legislation against unauthorized rave parties, introducing prison sentences for organizers and fines for attendees.

“Despite its illegal nature, the government has mobilized to ensure the safety of this event and limit any disturbances,” the prefecture said.

Philippe Le Moing Surzur, the local prefect, said the site was “extremely dangerous due to the unexploded ordnance it may contain.”

While modern shells posed no threat, he warned of the risk from older unexploded ordnance dating back to World War II.

Old artillery shells

He said that even the France’s Directorate General of Armaments, which owns the land, did not have precise knowledge of the risks.

“This is a site that has been in use for 150 years, and we know there are potentially old artillery shells there,” he said, adding that bomb disposal experts discover them regularly.

The firing range covers 10,000 hectares and is crisscrossed by roads that are closed during tests but open to the public at other times.

Signs prohibit access to the range itself, but it is not fenced off.

The organizers have urged attendees to refrain from lighting fires, digging or picking up any objects.

The local mayor’s office said residents and partygoers were getting on well.

“For once there’s something going on, make the most of it!” Paulette, 64, who lives in the village nearby and declined to give her family name, told AFP.

Emergency services treated 12 people with minor injuries Saturday morning.