At least 14 people have been killed and 15 others injured in the third deadly fire in Paris in less than two weeks.
The victims are thought to have died from inhaling toxic fumes
The blaze ripped through an 18-storey building in the southern Val-de-Marne area of the French capital.
The apartment building was not used to house immigrants, as was the case in last month's fires in the city.
Detectives believe the fire was started deliberately and people were reportedly seen setting light to letterboxes. Four people have been arrested.
The blaze was quickly put out by some 160 fire-fighters, but people were mainly killed by the fumes, according to officials.
French Prime Minister Dominique de Villepin has promised a full investigation.
Local Mayor Patrick Seve said the death toll included three children, and warned it could rise.
One woman gave birth at the scene right after being rescued, and was then taken to hospital with her baby.
The building, in the L'Hay-les-Roses suburb, housed some 500 people.
It dates back to the 1970s, but had been recently renovated.
The blaze came only a few hours after thousands of people marched through Paris in protest at the two previous fires nearer the city centre, which killed many African immigrants.
The protesters demanded better housing.
The French authorities have been criticised for housing poor immigrants in inadequate accommodation.
The march began at the site of the first fire in Paris' 13th district, in which 14 children and three adults died on 26 August.
Seven people died in a similar blaze in a dilapidated building four days later.
Sunday's fire was the fourth in less than five months in the Paris area.
In April, 21 died when a fire destroyed a budget hotel in the centre of the city.
RECENT DEADLY PARIS FIRES
1. 15 April: Blaze at Paris-Opera hotel kills 24
2. 26 August: Fire in 13th district kills 17, including 14 children
3. 30 August: Seven die in Marais fire, including four children
4. 4 September: At least 14 die in L'Hay-les-Roses suburb