Three relatives of Mohamed Lahouaiej Bouhlel are Islamic extremists who were jailed in Tunisia. They are understood to be brothers and cousins of Bouhlel’s wife. Police sources said two of them were arrested in 2008 for training with weapons in the mountains. One said: ‘After release, one, who we think is extremely dangerous, went to Syria, and we are checking if one was in Nice, but he definitely flew to Europe from Tunisia. The third man usually lives here but we haven’t traced him.’