16 dead, 3 missing after flash floods ravage southeast France (PHOTOS, VIDEOS)
"It's not over," Hollande said, as cited by AP.
Local officials and emergency services had earlier given conflicting casualty estimates.
On Saturday evening, the disaster hit the Alpes-Maritimes region, which borders Italy on the Mediterranean coast.
Over a period of just three hours, twice the average monthly amount of rain poured down.
Torrents streamed into several cities, washing away cars, and some local rivers broke their banks.
Three people from the same family died in their car near the town of Vallauris. They were in a tunnel that rapidly filled with water.
A few more people died in an underground car park, as they were trying to get their cars out. Rescuers still don’t have access to their bodies.
Three elderly people were killed near Antibes, when a ground-floor room where they were sleeping was engulfed.
Floods also devastated a camping site in the Antibes area, where a tourist died.
Rescue forces warn there may be much more casualties, as some areas remain inaccessible. Torrential rain tore away asphalt and roads were inundated with streams of mud.
The flooding also led to the closure of the A8 motorway connecting France with Italy.
Railway links have also been damaged: a TGV express at the Nice train station was flooded, with hundreds of people spending the night in the train. The station in the resort town of Cannes has also been shut down.
Over 70,000 households were left without electricity, but currently power has been restored to half of them.
In Nice, a soccer match in the French first division was abandoned midway.
President Francois Hollande has expressed his condolences to the victims’ families, and all measures necessary will be taken to restore stability in the region.