The Bastille Day truck massacre killed 84 people. (File Photo)
French police found a Kalashnikov rifle and a bag of ammunition in the basement of a man held in connection with the Bastille Day truck massacre, a source close to the case said.
The raid was carried out as part of the investigation into a 22-year-old man believed to have received text messages from Mohamed Lahouaiej Bouhlel on the night of the attack, discussing the supply of weapons.
About 100 investigators are poring over masses of data linked to the probe, and photos found on Bouhlel's cellphone indicate he was studying several locations where crowds gathered.
One photo concerns a fireworks display on August 15, another a race on January 10 along the Promenade des Anglais where the attack took place, and another showed the opening times of the fan zone during the Euro football tournament.
Jean-Pascal Padovani, the lawyer for the 22-year-old suspect, has denied "any implication in a terrorist act" by his client.
Five suspects will go before anti-terrorism judges investigating the attack that left 84 dead and over 300 injured.
They are four men aged 22 to 40 and a women aged 42 who were linked to Bouhlel, who was shot dead by police after he ploughed a rental truck into a crowd of people.