Ten people, including five children aged three to 15, were killed in a fire in the early hours of Friday in a residential building in Vaulx-en-Velin, near the French city of Lyon, Interior Minister Gerald Darmanin said.
Another four people were seriously injured in the fire, which started on the ground floor before spreading up the seven-storey building, rescue authorities told local media.
The fire is now extinguished, but footage on social media showed a huge, dark cloud billowing above the building earlier in the day.
The blaze occurred around 3:00 am (0200 GMT).
"I was awakened by the screams," a neighbour, Mohamed, told Le Progres de Lyon newspaper. "We wanted to help people but the smoke was too heavy. I saw a dead woman ... It's dramatic."
Darmanin said the cause of the fire was not known at this stage.
"There are several scenarios and a probe will be opened," said the minister, who is heading to the site.


Wave of bomb threats afflict European flights for third time this week
Jay Rockefeller, heir to famed dynasty and former US Senator, dies at 89
At least two children killed in bus crash in eastern France, authorities say
Vance repudiates Iran war after US electoral defeat
Malaysia ex-PM Najib Razak set for house arrest after party pays fine to leave jail
