At least 40 people are dead and 115 injured, many of them seriously, after the violent fire that broke out on New Year's Eve.
A spokesman for the University Hospital of Geneva told the BBC that patients as young as 15 were being treated for severe burns. Stéphane Ganzer, head of security in the canton of Valais, told BFM television that many of those being treated in hospital were unidentified.
The Le Constellation bar is described as a popular meeting place for tourists and young people. Many foreign nationals are believed to be among the victims. Italian authorities say 13 Italians are being treated in hospital and six are missing. The French Foreign Ministry says nine nationals were injured and eight are missing.
According to Swiss investigators, it could take days or weeks before all the victims are identified.
Panic and chaos
Witnesses describe panic and chaos as the New Year's celebration suddenly turned into a fire inferno, with people desperately trying to break windows to escape the flames. Others managed to escape the blaze.
Relatives are now desperately searching for missing friends and family members.
Laetitia, whose 16-year-old son Arthur was at the bar, told BFM: "I will continue to look for him, I will not give up."
An Instagram account shares photos of missing people. They are mainly young people, some born as recently as 2011.
"We have tried to get hold of our friends. We have taken lots of pictures and put them on Instagram, Facebook, every social media outlet imaginable, to reach them," 17-year-old Eleonore told AFP.
"But there is nothing, no answer," she continued.
The cause of the fire has not been determined. Several media outlets are reporting, citing witnesses, that sparklers or ice torches in champagne bottles may have caused it.
“Bottleneck at the stairs”
19-year-olds Nathan and Axel were in the bar's basement and described to Swiss Blick how someone waved a bottle of sparklers that came into contact with the ceiling - which caught fire.
"Everyone wanted to get out, but there was a bottleneck at the stairs," Axel told the newspaper.
The friends managed to escape by smashing a window with a table.
It is unclear how many people were at the bar, which, according to AFP, has a capacity of 300 people indoors.
Swiss President Guy Parmelin has announced five days of national mourning.
