An official at the Paris prosecutor's office says that a man has been detained and handed preliminary terrorism charges for posing in a photo with the Nice truck attacker.

Agnes Thibault-Lecuivre said the 36-year-old man was placed in custody Monday for "criminal terrorist association," after authorities found the photo of him with driver Mohamed Lahouaiej Bouhlel in front of the truck used to carry out the attack.

Authorities suspect him of ties to Bouhlel, who drove the truck down a busy pedestrian walkway on Bastille Day before being shot dead by police. The man is the sixth person detained over the heinous attack that killed 84 people last month.

France continues to be on high alert after the killing of an 85-year-old priest by two jihadi attackers last week.