A fire swept through a Friday night birthday party at a bar in the Normandy city of Rouen, killing at least 13 people and injuring six others, French authorities said.
More than 50 firefighters battled the blaze at the bar in the city centre, said French interior minister Bernard Cazeneuve.
He gave an initial count of 13 dead and six injured in the fire, which started after midnight Friday.
The prefecture, which runs the region, said one of the six injured was in life-threatening condition.
A judicial inquiry has been opened to determine the cause of the blaze, Cazeneuve said in a statement.
The local Paris-Normandie newspaper said the fire ignited in the basement of the Cuba Libre bar, which was rented for the evening for the birthday celebration.
The paper, without citing sources, said the ceiling quickly ignited when candles were lit. The ceiling was covered in special isolation material against sound.
The paper quoted the deputy prosecutor present at the site as denying initial reports of an explosion. Laurent Labadie was quoted as saying that the noise reported by neighbors would have been the sound of windows exploding from the heat.
The neighborhood was blocked off, and Rouen mayor Yvon Robert was on the scene.
A tense France is on maximum terror alert after two attacks last month, the latest the killing of a priest in his church outside Rouen. The funeral Mass was held at the Rouen cathedral on Tuesday.