Reports saysay 10 people, including a baby, have died in a fire at an eight-storey building in south-western Paris.
Nearly 30 people, including six firefighters, were injured.
One person is in a serious condition.
It is not clear what caused the blaze in the upmarket 16th arrondissement near the Parc des Princes soccer stadium.
The Paris prosecutor says it may have been deliberately started.
Police have detained a female suspect.
While the fire was raging, a police source says she was suspected of trying to set fire to a car parked nearby.
The suspect, who lived in the building, was reportedly drunk and is said to have justified her actions as the result of a conflict with a neighbour.
The fire is now under control but the death toll could still increase.
The fire spread across the two floors of the 1970s building shortly after 01:00 (00:00 GMT), forcing some residents to scramble on to nearby rooftops to escape the flames and smoke.
About 250 firefighters were deployed to the scene not far from the Bois de Boulogne Park, helping to rescue those trapped on the roofs.
Just a few weeks earlier, four people were killed after a huge blast at a bakery in the centre of the city.