BBC – The 32-year-old man of Algerian descent was one of two brothers detained in the south-east town of Vienne on Thursday.
Police believe they had been in contact over the internet with people linked to al-Qaeda in the Islamic Maghreb, and had been planning attacks in France.
Cern’s Large Hadron Collider is aiming to recreate conditions of the Big Bang.
The organisation confirmed that a physicist working at its site had been arrested “under suspicion of links to terrorist organisations”, and said it was helping the French police with their investigation.
