Flooding from record rains in the mountainous region that spans France and Italy killed two people in Italy and left at least 24 people in the two countries missing Saturday.
A storm that moved overnight across southeastern France and then northern Italy caused major flooding on both sides of the border, destroying bridges, blocking roads and isolating communities.
In Italy, a firefighter was killed during a rescue operation in the mountainous northern region of Val d'Aosta. Another body was found in Vercelli province, near where a man had been swept away by flood waters late Friday.
A total of 16 people were reported missing in Italy, all but one travelers in cars on the Col de Tende high mountain pass between France and Italy, according to civil protection authorities.
They include two people from Germany driving with their 11-year-old and 6-year-old grandchildren, and a pair of brothers returning from France.
The spokesman for Italy's firefighters said a search was ongoing for a missing shepherd who was pulled into flood waters on Col de Tende. His brother managed to grab onto a tree and was saved, while authorities were searching on the French side for the shepherd.
Firefighter spokesman Luca Cari said he suspects the other people reported missing in Italy have lost phone contact, but at the moment they are not thought to be in imminent danger.
The situation at the tunnel on the high mountain pass is complicated by the fact that French emergency responders cannot access their side due to flood damage, Cari said. Italian firefighters were searching the French side for people who may have been blocked.
Unrelenting rainfall overnight hit levels not seen since 1958 in northern Italy's Piedmont region, where as much as 630 millimeters (24.8 inches) of rain fell in a 24 hour period, according to the Italian civil protection agency.
Hundreds of rescue operations were underway. Eleven campers were saved in Vercelli province, where floodwaters hit 20-year highs. And Alpine rescue squads have evacuated by foot seven people who were in houses cut off by flooding at Terme di Valdieri; some had to be carried on stretchers due to the muddy conditions and accumulation of detritus.
On the other side of the border, in southeastern France, almost a year's average rainfall fell in less than 12 hours in the mountainous area surrounding the city of Nice. Nice mayor Christian Estrosi said over 100 homes were destroyed or severely damaged in the area.
French Prime Minister Jean Castex, who flew over the area in an helicopter, confirmed that at least eight people were missing, including two firefighters whose vehicle was carried away by water when the road collapsed during a rescue operation.
``I cannot hide our grave concern on the definitive toll,'' Castex said.
Many worried families had not heard from their relatives due to cellphone services being cut off in the area.
``As I speak, priority goes to searching for victims, providing supplies and accommodation for the people affected, and restoring communications,`` the prime minister said.
Rescue efforts included 871 personnel working on the ground, as well as military helicopters and troops helping with emergency assistance, Castex said.
French President Emmanuel Macron on Saturday expressed gratitude toward rescuers on Twitter. ``Together we will get through this,'' he said.
France's national weather agency, Meteo France, said that up to 500 millimeters of rain (19.7 inches) were recorded in some areas, the equivalent of almost one year of average rainfall.
Meteo France issued a danger alert on Friday and all schools in the region had been closed. Local authorities urged people to stay at home.
In central Switzerland, flooding along the Reuss River caused the closure of a stretch of the A2 highway - a major trans-Alpine route. Further east, 13 residents were evacuated from their homes in the town of Diesbach because of flooding.