Seven bodies have been found in a region straddling the French-Italian border near Nice after torrential rains swept houses and roads away.
Around 1,000 firefighters, four military helicopters, and troops were mobilised in France to help search for the missing people in the mountainous south-eastern region after the devastating floods.
Officials said five of the bodies were discovered in north-western Italy, including four washed up on the shore between the towns of Ventimiglia and Santo Stefano al Mare, near the French frontier.
Some of the bodies might have been swept down the coast from France.
Two more were found in France, including a shepherd found by an Italian search and rescue team.
The other body was found in a vehicle that had been swept away by flash-flooding in the village of Saint-Martin-Vesubie.
It brings to nine the total number of people found dead after fierce rains and howling gales lashed the border area on
Floods washed away houses and destroyed roads and bridges surrounding the city of Nice on the French Riviera after almost a year’s average rainfall fell in less than 12 hours.
Nice mayor Christian Estrosi said more than 100 homes had been destroyed or severely damaged.
French firefighters said another 21 people were missing, eight of them known to be as a direct result of the storm.
Rescuers were also providing emergency assistance, including food and water, to residents living in isolated villages.
Authorities fear there could be more victims, as many families could not contact relatives due to mobile phone services being down.
French Prime Minister Jean Castex, who flew over the area in a helicopter, expressed “grave concern” over the toll of the flooding.
About 10,500 homes were left without electricity.
In Italy, a firefighter was killed during a rescue operation in the mountainous northern region of Val d’Aosta.
A search team also found a body in the Piedmont region’s Vercelli province, where a man had been swept away by floodwater.
Italian firefighters also rescued 25 people trapped on the French side of a high mountain pass due to the flooding.
A total of 17 people have been reported missing in Italy, mostly travellers in cars on a high mountain pass.