Some 16 people, including 10 police officers and a firefighter, were also slightly hurt in the blaze in the north-eastern Paris suburb of Aubervilliers, according to the fire service.
The fire took hold in the attic of a building with two floors.
According to a police source, people used windows to escape the flames while others sought refuge on the roof.
The cause of the blaze remains unknown, the fire service added.
Paris firefighters tweeted a picture of rescue operations once the flames were put out.
"Aubervilliers is once again touched by a serious fire," the town's mayor Meriem Derkaoui said on Twitter, adding that the site of the fire was a private residence but that the town needed to look into the conditions of its occupation.
Aubervilliers touchée par un grave incendie dans une habitation privée dont les conditions d'occupation restent à éclaircir. Je salue le courage des @PompiersParis et l'action des services municipaux. Mes pensées vont aux victimes et à leurs famillesMeriem Derkaoui (@Meriem_Derkaoui) August 19, 2018
In the same town less than a month ago, a fire in a housing complex killed a mother and her three children aged 18 months to six years, and left nine others injured.