French police conducted a counter-terrorism operation in the Argenteuil area north of Paris Thursday near a mosque and an Islamic library, authorities said.
It is not yet known whether the operation had any links to last week's truck attack in Nice.
Meanwhile, France's interior minister said that there were no national police stationed at the entrance to the walkway in Nice when the Bastille Day truck attack took place.
Bernard Cazeneuve's acknowledgement Thursday came as a newspaper accused French authorities of a lack of transparency for their handling of the massacre.
Cazeneuve initially had said that “national police were present and very present on the Promenade des Anglais” and suggested that their cars were blocking the pedestrian sidewalk entrance, in a speech two days after the July 14 attack that killed 84 people and injured several dozen.
Cazeneuve launched an internal police probe into security measures taken for the Bastille Day celebrations in Nice shortly after Thursday's backtrack.
Speaking from Dublin where he met the Irish prime minister, French President Francois Hollande said the conclusions of the investigation will be known next week.
Hollande said that any police “shortfalls” will be carefully looked into, but defended French authorities against the media attacks, saying that “there is no room for polemics, there is only room for transparency.”
His comments came in response to French newspaper Libération's accusations that Cazeneuve lied about the presence of the national police officers and cars and authorities lacked transparency about the attack.
Five detained suspects with possible links to the attack were to appear before anti-terrorism judges Thursday, who will decide whether to charge them.
In a related development, France's lawmakers voted Wednesday to extend the state of emergency for another six months, continuing greater police search-and-arrest powers without advance clearance from judges.
Speaking in the lower house of parliament (the National Assembly), French Prime Minister Mannuel Valls said that the fight against terrorism would be long and difficult, warning against a social divide with millions of Muslim citizens.
"We must protect all our compatriots," he said. "We should of course also protect our Muslim compatriots, the co-citizens, the compatriots, co-citizens of Muslim culture, who today are also afraid, and feel blamed and who see the considerable damage not only from the attack, but also from what IS [so-called Islamic State] is trying to do to fracture French society."
Paris officials cancelled some summer events, including open-air free movie showings and a car-free day on the city's famous Champs-Elysees boulevard.
The move followed the attack last week in Nice by a French-Tunisian, 31-year-old Mohamed Lahouaiej Bouhlel, who drove a truck through crowds celebrating Bastille Day.
No official list of the dead has been released but it is known they include French, Americans, Germans, Ukrainians, Swiss, Tunisians, Polish and a Russian nationals.
French general prosecutor Francois Molins has labeled the unprecedented rampage a terrorist strike by a man who had shown support for the Islamic State group and searched online for information about the attack on a gay nightclub in Orlando, Florida.
Islamic State has claimed responsibility for the attack, although there is no evidence linking Bouhlel to the group.
France imposed emergency rule after the November 13, 2015 attacks carried out by Islamist militants that claimed the lives of 130 people in Paris and left scores of others wounded.