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.