French truck killer Mohamed Lahouaiej Bouhlel was helped to prepare his Bastille Day attack by five suspects who are now in custody, prosecutor Francois Molins said on Thursday.
Molins said the four men and a women were "involved in the preparation" of the attack, which had been planned months in advance.
More than 400 investigators have been poring over evidence since the July 14 attack in which Bouhlel rammed a truck into crowds on the Nice promenade, leaving 84 dead and over 300 injured.
Molins said that one of the suspects had filmed the scene of the crime the day after the carnage, as it crawled with police and journalists.
The five suspects will be presented to anti-terrorism judges later Thursday and Molins said prosecutors had requested they be charged with conspiracy to commit terrorism, among other crimes.
Bullet impacts are seen on the heavy truck that was driven into a crowd at high speed in Nice last week.