French Interior Minister Bernard Cazeneuve gave an initial count of 13 dead and six injured. He says more than 50 firefighters are battling the blaze in the center of the city.
The fire started late Friday night or shortly after midnight. A judicial inquiry has been opened. One source close to the investigation told the AFP news agency that candles on a birthday cake may have sparked the blaze. The ceiling quickly ignited when candles were lit.
At least one of the injured was in a critical condition, the secretary general of the Seine-Maritime prefecture Yvan Cordier said.