Greenpeace activists invaded a French nuclear power plant site before dawn Monday _ a media stunt that deeply embarrassed the government as it was carrying out a safety review of France's crucial atomic energy sites.
In one of at least four near-simultaneous attempts to invade nuclear sites across France, nine activists sneaked into one plant in Nogent-sur-Seine southeast of Paris. Some scaled a domed containment building above a nuclear reactor to hoist a banner that read "safe nuclear doesn't exist" and paint an exclamation point, evoking danger, on the rooftop.
President Nicolas Sarkozy derided the "rather irresponsible" risks to lives, yet the guerilla-style tactics immediately stoked concerns about the vulnerability of France's nuclear facilities to terrorists or any other would-be invaders.
France is a big supporter of nuclear power and gets about three-quarters of its electricity from it, more than any other nation. It regularly faces protests from environmental activists over shipments of nuclear waste, but activist incursions into atomic plants are unusual.
Greenpeace said its break-in aimed to show that a review of safety measures _ ordered by French authorities after a tsunami ravaged Japan's Fukushima Dai-ichi nuclear plant in March _ was focused too narrowly on possible natural disasters and not human factors.
Sarkozy promised full "transparency" about the safety of nuclear facilities in France in the final report.
Activists who tried to enter three other French nuclear sites Monday were prevented from doing so, but Greenpeace said other invaders were still holed up inside other, unspecified, nuclear sites. The environmental group even posted a video on its website of one whispering activist said to be speaking from inside a nuclear site under what looked like a white tent.
That prompted French authorities to immediately launch a "thorough sweep" of all of France's 20 nuclear power plants, Interior Ministry spokesman Pierre-Henry Brandet said by phone, adding that Interior Minister Claude Gueant scheduled an emergency meeting this week to review the security breach.
The French power company Electricite de France, which operates the site, denounced the "illegal" break-in at Nogent-sur-Seine.
After Greenpeace alerted authorities that its activists were behind the incursion, police and security teams held their fire and allowed the activists to continue scaling a containment building that houses the reactor to put a banner on top, Brandet said. The activists didn't penetrate the reactor and all nine were arrested within hours.
EDF said activists' banners were also hung on the outside of two other nuclear sites _ Chinon in northwestern France and Blayais in the southwest _ before they were removed. Three other activists were driven off by security forces while trying to enter yet another plant, in southeastern Cadarache.
"We have to understand what's behind this malfunction _ notably in Nogent," Brandet said, adding that "in the other sites security worked ... the intrusions were thwarted."
EDF said it had no indication of intrusions at other sites in France.
"With this nonviolent action, Greenpeace has shown how vulnerable French nuclear plants are," said Sophia Majnoni d'Intignano, a Greenpeace activist. "Simple activists, with peaceful intentions and of few means, were able to reach the heart of a nuclear plant."
French TV showed pictures of activists in miner's helmets rummaging through the dark and crawling in what appeared to be a tunnel with banners that read "Coucou" (Hey) and "Facile" (Easy) on them.
Majnoni d'Intignano predicted the government was going to conclude in the review that "our nuclear plants are very, very safe, because it's believed that they could withstand a flood or an earthquake," she told i-Tele television.
"But those aren't the real risks for our nuclear industry," Majnoni d'Intignano said. "It's the risk of external, non-natural attack _ like the risk of terrorism."
Speaking by phone with The Associated Press, she urged the government to consider other risks in its review like an airplane crash, a computer virus, or a chemical explosion at a nuclear site.
"It's a very limited review _ they have badly understood the signal sent from the Fukushima incident," she said. "For us, the real risks are human and technological."
Nuclear officials sought to play down the incursion's impact.
"A nuclear plant is a bit like a Russian doll: they got through one layer, then a second layer of security, but they didn't get to the sanctuary layer," Francis Sorin, a spokesman at the French Nuclear Energy Society, told BFM television.
Sarkozy said last month it would be madness for France to reduce its reliance on nuclear power, despite worldwide wariness after the Fukushima disaster and recent European protests over the dangers of nuclear waste.
Nuclear power has also increasingly divided the French left, with six months left before France's next presidential election.
The nominee of the main opposition Socialist party, Francois Hollande, has pledged to shut down more than 20 reactors _ the boldest proposal for any mainstream French party in the nuclear era. Still, his Green party allies are pushing for more concessions.
But even French officials were acknowledging the incursions had an impact.
"It still makes you think about the security of access to nuclear plants ... I think we'll have to learn some lessons," Henri Guaino, a special adviser to Sarkozy, told BFM.
Associated Press writer Sylvie Corbet contributed to this report.