Investigators continue to work at the scene near the heavy truck that ran into a crowd at high speed killing scores who were celebrating the Bastille Day July 14 national holiday on the Promenade des Anglais in Nice, France, July 15, 2016. REUTERS/Eric Gaillard

PARIS (Reuters) - Two more people have been arrested in connection with the Nice attacker who killed 84 people in the French Riviera city of Nice on July 14, sources close to the investigation told Reuters on Tuesday.

Paris prosecutor Francois Molins said last week the Bastille Day attacker, Mohamed Lahouaiej Bouhlel, had been planning the attack for months. Five suspected accomplices already in custody have been put under formal investigation.

None of the five had been known to intelligence services.

The source said the new arrests took place on Monday in Nice.

A second source said the two arrested were men and that their pictures had been found on Bouhlel’s mobile telephone.

In an attack claimed by Islamic State, the 31-year-old Tunisian plowed his hire truck into a crowd of revelers along Nice’s palm-fringed Promenade des Anglais.

The militant group called Bouhlel one of its soldiers, but authorities say they have yet to find evidence that the 31-year-old, who was shot dead by police, had any actual links to the militant group.