Flammable sound-proofing material is likely to blame for the rapid spread of the deadly fire at a Swiss ski resort, Sky News has been told.

The disaster occurred during the early hours of Thursday at Le Constellation, a bar in the upmarket Alpine ski resort of Crans-Montana.

At least 40 people died in the fire and 119 were injured, with several of those hurt in the blaze still in a life-threatening condition.

Swiss President Guy Parmelin has described the fire as "one of the worst tragedies our country has ever experienced".

Here is all we know so far.

Follow latest: 'Around 40 people' killed in Swiss ski resort fire

Image: Photo shows woman on shoulders with sparklers in bottle before fire

What happened?

The incident occurred at roughly 1.30am local time (12.30am UK time) while guests were celebrating the start of 2026.

Seconds after noticing the smoke, a witness contacted police, and the first officers had arrived by 1.32am, Valais Canton police commander Frederic Gisler said in a briefing on Thursday.

The fire appeared to spread voraciously, prompting people to surge up a staircase towards an exit. Witnesses reported people screaming, climbing over each other and smashing windows in panic to escape.

People outside described victims emerging with their hair or clothes burned off, and likened the scenes to a horror film.

Many of the victims are young people. Almost 120 more have been injured, with some remaining in a life-threatening condition.

What caused the Swiss bar fire?

On Friday, officials tentatively confirmed the theory that had been circulating about the cause of the fire.

Valais attorney general Beatrice Pilloud said it "would appear" that the fire started from "sparkler candles, otherwise known as flares, which were placed on top of champagne bottles".

She added: "These flares were taken too close to the ceiling. This led to what is referred to as a flashover incident, where the fire spread very rapidly."

Two French women who claim to have escaped from the burning venue told BFMTV on Thursday: "In a few dozen seconds, the whole ceiling was on fire. Everything was made of wood."

But Ms Pilloud asked people not to speculate about a type of foam thought to have been on the ceiling and that may have enabled the fire to balloon so quickly.

She said: "The investigation will seek to determine whether this foam was for safety, compliance and whether it is the cause of the fire or not."

'Not at all fire-resistant'

Retired London Fire Brigade Commander Steve Dudeney worked in the fire service for 31 years and is now a fire safety consultant.

He told Sky News: "What you've got there is polyurethane foam, a sound-deadening material. I mean, effectively it's not at all fire-resistant...

"In fact, it's an organic hydrocarbon, so it's very flammable_._

"Once it's on fire it will disintegrate, drop, you'll have flaming droplets come off of it and it will spread a fire rapidly.

"So anywhere that's got that, anywhere on the walls or ceilings should have nothing like any type of naked flame anywhere near it."

What is a flashover fire?

Swiss officials called the blaze an "embrasement generalise" or what English firefighters might call a flashover or backdraught.

Exact definitions vary, but a flashover refers to a fire triggered by the release of combustible gases that then ignite violently.

A backdraught describes an explosion that occurs when air reaches a fire in an enclosed space that has used up all the available oxygen.

In both instances the fire can explode at a surprising speed.

Image: Emergency teams survey scene of fatal resort bar fire

How many people have died or been injured?

On Friday officials updated the figures concerning people caught up in the fire.

The severity of the burns is making it difficult for officials to identify victims, and it also took time to remove all the bodies from the destroyed bar.

Valais local government chief Mathias Reynard said in a news briefing that 40 people are known to have died so far.

At least a further 119 people have been injured, many badly, and about half have been treated at the Valais Hospital. Some remain in a life-threatening condition.

The flames ripped through a ski resort bar Le Constellation, where people were celebrating in Crans-Montana.

Mr Reynard called the numbers "deeply troubling" and acknowledged the "unbearable wait" for families to find out what has happened to their loved ones.

Many of the victims were young people.

The major incident saw a total of 13 helicopters, 42 ambulances, 150 paramedics and 70 firefighters mobilised to help.

Leon Christe, who works in Crans-Montana, told Sky News he was one of the first to the scene and tried to help as many people as possible by administering first aid.

He said: "It was very chaotic and very sad. Everywhere, there were young people who needed help, some had their clothes burned off.

"It was very traumatising."

Image: Pic: AP

Where did the incident happen?

The bar is in Crans-Montana, in the Valais region at the heart of the Swiss Alps, which is popular with tourists from Britain and across Europe.

It is 40km (25m) north of the Matterhorn, one of the most famous Alpine peaks, and approximately two hours from the Swiss capital of Bern.

"This event took place in a place that is dedicated to life and joy... what an incredible and dreadful contrast," the Swiss president said on Thursday.

Sparklers likely caused Swiss bar fire

What are the nationalities of the victims?

Authorities have warned it may take "several days" to identify those who died due to the severity of the burns.

Young burn victims will suffer 'long lasting injuries'

A total of 113 of the 119 injured people have been identified, of whom:

• 71 are Swiss
• 14 are French
• 11 Italian
• 4 Serbian
• 1 Bosnian
• 1 Belgian
• 1 Portuguese

The identification of the dead is ongoing, and experts have resorted to dental and DNA records.

Swiss police are cooperating with the governments of France, Belgium, Poland, Portugal, Congo, Serbia, Turkey, Romania and the Philippines.

On Friday, the first victim was named as 16-year-old Italian Emanuele Galeppini.

The UK embassy in Switzerland said on Thursday it had "not been approached for assistance" but would "continue to monitor the situation".

Charlotte Niddam, who previously attended Immanuel College in Hertfordshire, has been identified as among the missing. Her nationality is unclear.