Editor’s note: This story contains descriptions and videos that readers may find disturbing.
As young partygoers celebrated the New Year in a packed bar in the Swiss Alps, the celebrations quickly turned into a nightmare as a devastating fire ripped through the basement, killing at least 40 people and injuring 119 others.
The Le Constellation fire in Crans-Montana has been described by the Swiss president as one of the country’s “worst tragedies”. As families anxiously await word that their loved ones are missing and experts work to identify victims, authorities are still trying to figure out how the fire started and why it spread so quickly.
Swiss authorities said on Friday that a champagne sparkler was the likely cause of the fire, but the official investigation is still ongoing. Newly released video and witness accounts reveal a deadly combination of fire-prone ceiling panels and a crowded bar packed with young patrons flocking toward narrow escape routes.
Le Constellation is located in the heart of Crans-Montana, an exclusive ski resort in the French-German canton of Valais, and is a popular nightspot among young locals and tourists.
Witnesses said around 200 people gathered inside the venue on New Year’s Eve, preparing to celebrate 2026 with music, drinks and dancing.
An image widely shared online showed a show staffer wearing a motorcycle helmet riding on someone else’s shoulder while holding a champagne bottle containing a sparkler in a packed crowd.
One clip shows at least six bottles being lifted into the air as flames and smoke billow from the ceiling.
The sparkler appears to have ignited what experts believe to be acoustic panels in the ceiling. Although this panel is designed to improve acoustics, it is also a highly flammable material.
Independent fire consultant Stephen McKenzie described it as “plastic petrol”, adding: “That’s why we’re seeing reports of so many young people suffering first-, second-, third- and, unfortunately, fourth-degree burns.”
Switzerland’s chief prosecutor Beatrice Pilou told reporters on Friday that investigators were looking into whether the bar had foam panels installed and whether they complied with regulations.
Once the fire broke out, it quickly spread.
One video shows a young man trying to put out the fire by hitting it with a cloth, while other videos show him recording on his cell phone and continuing to dance, seemingly unaware of the impending danger.
“Once the ceiling caught fire, within about 10 seconds the whole nightclub was on fire,” one witness said.
Another witness, Axel, who declined to give his last name, told Reuters News that he and others at the bar did not initially realize the danger was serious.
“We were screaming, ‘Fire, fire!’ and we thought it was a joke or it wasn’t necessarily serious, and then all of a sudden there was this huge plume of black smoke and we couldn’t breathe anymore,” he said, describing how he eventually got upstairs and broke a window to get out.
As smoke filled the lounge and a fire blazed, partygoers rushed toward the narrow staircase.
Footage reviewed by CNN showed dozens of people trapped in exits and one person jumping out of a window as thick red smoke filled the building.
McKenzie explained that the fire spread rapidly through a process called flashover, where almost everything in the room ignites at about the same time.
He said “burning progresses at ceiling level” and the fire “spreads laterally”. This process is like a “stone dropped into the sea”, the smoke ripples sideways and begins to “preheat” everything in front of it.
When the fire door opened, it could have created a “chimney effect” that accelerated the flow of smoke and flammable gases upwards, McKenzie said. “The smoke is actually burning — a ‘flashover,'” he added.
On Friday afternoon, Swiss prosecutor Pilou said all signs support this theory: “As things stand, everything points to the fire starting from a sparkler or a smoke bomb placed in a champagne bottle too close to the ceiling, quickly leading to a flashover fire.”
Laetitia Place, 17, who was attending the party from Lausanne, described her harrowing experience of fleeing the fire, saying there were collisions at narrow exits, making it difficult for others to get through.
“The first staircase was very easy to get through, as it was wide. But then there was a small door that everyone was pushing through, where we all fell and piled on top of each other. Some were on fire, some were dead next to us,” the teenager told Reuters.
Footage obtained by CNN shows people lying motionless outside and bystanders trying to help.
Local resident Samuel Rupp, 21, witnessed the aftermath.
“People were screaming and then there were people lying on the ground, probably dead.”
Swiss emergency services responded within minutes of the fire, transporting the injured to hospitals across Switzerland and abroad. Officials told reporters on Friday that about 50 patients have been or will be transferred to hospitals in other European countries for specialized treatment.
Edmund Coquette told CNN affiliate RTL Germany that he saw “bodies on the street” and young people with missing fingers and “completely burnt faces.”
A man who lives near Le Constellation and rushed to help people flee the burning building said he searched for an emergency exit behind the bar and found it jammed with people trying to get out. The man, Paolo Campolo, told French media outlet 20 Minutes that he had asked the fire chief for help, but soon decided to intervene himself.
“We didn’t wait. We broke the door open with whoever happened to be passing by and let people get out,” Campolo said from his hospital bed.
Dr. Robert Laribau, director of emergency care at Geneva University Hospital, told CNN that most of the patients the hospital has admitted are between the ages of 15 and 30, and many have “extremely serious injuries” from possible flashovers and backdrafts.
Flashover usually causes severe burns, especially to the face, back, and upper extremities, and is often accompanied by serious inhalation injuries from radiant heat and superheated gases. Backdrafts, which are oxygen explosions, can cause instant fatal burns and toxic inhalation.
Swiss authorities said on Friday that the bar’s two French owners were being interviewed by police to gather information, opening an investigation into the circumstances surrounding the fire and why it spread so quickly.
CNN has reached out to the bar owners through their companies, but has not yet received a response.
Meanwhile, as of Friday night, many loved ones of the victims and injured were still waiting for answers, and authorities continued to work to identify the dead.
CNN’s Martin Goilandeau, Billy Stockwell, Henrik Pettersson, Nick Robertson, Joseph Ataman, Duarte Mendonca and Camille Knight contributed reporting.
