A nuclear physicist working on the "large collider" experiment to simulate the Big Bang has been arrested in France on suspicion of advising al-Qa'ida on possible terrorist targets.
The 32-year-old French scientist, of Algerian origin, is being held with his younger brother after being trailed, and bugged, by French anti-terrorist police for more than a year.
A judicial source told the newspaper Le Figaro: "This is very high level." The French Interior Minister, Brice Hortefeux, said that the investigation "may perhaps show that we have prevented the worst".
The scientist – who was not immediately named – was arrested alongside his brother near Lyons on Thursday on suspicion of having contacts with al-Qa'ida in the Islamic Maghreb, or Aqim. He was said to have been suspected of giving advice on possible nuclear targets within France.
The suspect was one of 7,000 working on the Cern project on the Swiss-French border to build a Large Hadron Collider, with the aim of simulating some of the conditions of the Big Bang in an attempt to answer questions about the origins of the universe. Since its official opening last year, the 17-mile circular underground tunnel has mostly been closed for repairs.
French sources suggested to Le Figaro that he was not planning to threaten the collider itself. Officials at Cern added that the arrested scientist had no access to materials that could be used for terrorism. Cern emphasised that his work at the centre, on one of the smaller experiments linked to the collider, should not be cause for alarm. "None of our research has potential for military application, and all our results are published openly in the public domain," a statement said. The physicist had no access to the tunnel itself.
Le Figaro said that the French internal security agency, the DCRI, hoped the arrests would help European governments to dismantle an important al-Qa'ida network. Intelligence sources told the newspaper that the scientist had been under surveillance for 18 months after his name came up in the investigation of the so-called "Afghan network" of European terror groups.
Investigators also intercepted internet messages between the older of the two brothers and people identified as being linked to Aqim. The messages concerned possible French nuclear targets. Other judicial sources told Reuters that the men were believed to be planning attacks in France but no specific targets had yet been identified.
The advanced scientific qualifications of the older brother suggest that this was not "just a fantasy" but a real plot, intelligence sources said. Police seized two computers, three hard disks and several USB keys.
Mr Hortefeux recalled yesterday that Aqim and other terror groups had recently listed France among their possible targets. "We are on permanent alert and follow the declarations of certain groups day by day," he said. "We never drop our guard. The risk is permanent."