Paris ( CNN ) -- France 's interior minister admitted Monday that lapses in security made it possible for Greenpeace activists to gain entry to a nuclear power plant southeast of Paris . Interior Minister M. Claude Gueant said there have been lapses in the nuclear plant 's security system and has ordered a search of all nuclear plants , a spokesman for the ministry told CNN . The environmental activist group said on its website that members gained entry to the plant at Nogent-sur-Seine at dawn and managed to climb the dome of one of its two reactors `` in order to spread the message : 'Safe nuclear does not exist . ' '' `` This action shows how vulnerable the French nuclear centrals are : Peaceful activists have managed with a few means , to reach the heart of the nuclear central ! Why ? How ? Because the security device is insufficient , '' the website stated . President Nicolas Sarkozy , during a news conference with German Chancellor Angela Merkel , called the act `` irresponsible , '' but said that the government will `` absolutely publish all '' of the audits related to plant security .
Prime minister has ordered a closure of all nuclear plants , spokesman says . Greenpeace : Action on vulnerability of French nuclear security . French president calls it ` ` irresponsible '' but pledges cooperation .