This includes the suspected attacker, according to French authorities.
Two people were wounded in Friday’s stabbing - a man and a woman working at a documentary production company who had stepped outside for a cigarette break.
Officials have said their injuries are not life-threatening.
Counter-terrorism officers are investigating what authorities have called an Islamic extremist attack linked to Charlie Hebdo, which lost 12 employees in an al-Qaida attack in 2015.
Eight people had been detained in total after the stabbing on Friday, but one has since been released, according to judicial sources.
Five of those in custody were detained in the Paris suburb of Pantin in a residence where the suspect is believed to have lived, a police official said.