A 47-year-old man is in police custody in Nice, suspected of having been in contact with the assailant the day before the knife attack, BFMTV reported.
According to BFMTV citing a police source, the man was detained on Thursday evening. There is no information about the identity of the detained man.
The report comes amid an inquiry launched by law enforcement to find out whether the attacker had accomplices.
Following the tragic incident, France activated its counter-terrorism plan known as Vigipirate.
On the morning of 29 October, three people were killed in a knife attack at a church in Nice. According to Nice Mayor Christian Estrosi, the assailant continued to shout "Allahu Akbar" even as he was detained by police. French President Emmanuel Macron called the incident "an Islamist terrorist attack", and noted that the suspect is currently in police custody.