About 40 people were killed and another 115 injured, most of them seriously, during a New Year’s celebration in a Swiss Alpine bar, according to the police.
Authorities did not immediately have an exact count of the deceased.
A fire ripped through a crowded bar in the luxury Swiss ski resort town of Crans-Montana as revellers rang in the New Year.
Police, firefighters and rescuers rushed to the popular resort, one of the top-ranked ski destinations in Europe.
Two women who were in the bar told French broadcaster BFMTV that they saw a male bartender lifting a female bartender on his shoulders as she held a lit candle in a bottle.
"The flames spread, collapsing the wooden ceiling," they told the broadcaster.
One of the women described a crowd surge as people frantically tried to escape from a basement nightclub up a narrow flight of stairs and through a narrow door.
Another witness speaking to BFMTV described people smashing windows to escape the blaze, some gravely injured, and panicked parents rushing to the scene in cars to see whether their children were trapped inside.
The young man said he saw about 20 people scrambling to get out of the smoke and flames and likened what he saw to a horror movie as he watched from across the street.
Officials described how the blaze likely triggered the release of combustible gases that ignited violently and caused what English-speaking firefighters call a flashover or backdraft.
“This evening should have been a moment of celebration and coming together, but it turned into a nightmare,” said Mathias Reynard, head of the regional government of the Valais Canton.
The injured were so numerous that the intensive care unit and operating theater at the regional hospital quickly hit full capacity, Reynard said.
Crans-Montana is less than 5 kilometers (3 miles) from Sierre, Switzerland, where 28 people, including many children, were killed when a bus from Belgium crashed inside a Swiss tunnel in 2012.
The hospitals in Wallis were full and had declared a state of emergency, with the injured being transported to various hospitals across Switzerland.
The Le Constellation has a capacity of 300 people and another 40 people on its terrace, according to the Crans-Montana website.
Earlier, a police spokesman told AFP some 100 people had gathered there for New Year celebrations.
Ambulances were still parked outside the bar hours later, and broken windows could be seen.
Local media described a "smell of burning still in the air."
The "fire of undetermined origin" broke out in a bar popular with tourists, police in the Wallis canton in southwestern Switzerland said in a statement.
Investigators were working to determine the cause of the fire, police said.
A tourist from New York filmed bright orange flames pouring from the bar, and told AFP he saw people running and screaming in the dark.
"Several people lost their lives and others were injured," the police statement said, describing the incident as "serious" and adding that "a major emergency response is underway."
"A large contingent of police, firefighters, and rescue workers immediately went to the scene to assist the numerous victims," it said.
"The operation is still ongoing."
Swiss media suggested that the fire may have started when pyrotechnics were used during a concert, but police siad the cause was unknown.
Authorities said it was too early to provide an exact number of casualties, but said that since Crans-Montana is popular with tourists around the world, they expected them to include a number of nationalities.
At least two French citizens were among the injured, according to initial reports from the French foreign ministry.
Swiss media suggested that the fire may have started when pyrotechnics were used during a concert.
Police said the area was "completely closed to the public", and that "a no-fly zone over Crans-Montana has been imposed."
"The party was in full swing... music and champagne flowing freely," a resident who said they lived nearby told 24 heures, a Lausanne newspaper.
But as news of the fire broke, they said, the carefree mood vanished and people began gathering in the street. "We could hear the sirens in the distance. Around me, people were stunned, worried, silent."
"We heard helicopters all night long," another neighbour told 24 heures.
"With the fireworks, we didn't understand what was going on at first. Then we saw the smoke. It's terrible, a lot of young people go to that bar."
The community is in the heart of the Swiss Alps, just 40 kilometers (25 miles) north of the Matterhorn, one of the most famous Alpine peaks, and 130 kilometers (81 miles) south of Zurich.
The highest point of Crans-Montana, with a population of 10,000 residents, sits at an elevation of nearly 3,000 meters (1.86 miles), according to the municipality’s website, which says officials are seeking to move away from a tourist culture and attract high-tech research and development.
The municipality was formed only nine years ago, on Jan. 1, 2017, when multiple towns merged. It extends over 590 hectares (2.3 square miles) from the Rhône Valley to the Plaine Morte glacier.
(With inputs from AFP and AP)