A former pupil at a British private school is among the missing after a fire tore through a crowded basement bar at a Swiss ski resort on New Year’s Eve, killing at least 40 people.

As the scale of the disaster at Le Constellation bar in the resort of Crans-Montana became clear, families of teenagers made desperate appeals for information.

Charlotte Niddam, believed to be 15, has not been heard from. A former pupil at Immanuel College, a private Jewish school in Bushey, Hertfordshire, she also attended the JFS school in Harrow, London.

Footage filmed inside the bar has shown the moment the ceiling caught fire. Partygoers lost crucial seconds to escape by continuing to film as it took hold.

Investigators believe that candle-style sparklers of the type often used at parties were put in champagne bottles during the New Year celebrations and set the basement ceiling alight.

The authorities are also examining whether soundproofing material on the ceiling complied with fire safety regulations. If the investigation concludes that there are grounds to suspect negligence, the bar’s owners may face charges including for negligent homicide.

A person on another's shoulders, holding two bottles of sparkling wine with roman candle fireworks, at a bar in Crans Montana.

Footage from the bar immediately before the fire broke out

The French co-owners of the bar, Jacques and Jessica Moretti, have been interviewed by police. They are being questioned over both the ceiling materials and the emergency exits.

• Jacques and Jessica Moretti renovated Le Constellation bar themselves

Jessica Moretti, owner of the bar in Crans-Montana "Le Constellation".

A total of 119 people, most of them in their teens and twenties, were injured, according to the latest figures released by Swiss officials.

Charlotte had moved back to France with her family and was working as a babysitter for families in the resort. On New Year’s Eve she shared a video of herself online with the caption “until next year”.

A spokesman for Immanuel College said: “We are reaching out with an urgent request for our school community to come together in support of Charlotte Niddam. Charlotte was a student at Immanuel College, and her family have now moved back to France.

Charlotte Niddam, 15, who has been missing since the fire at Le Constellation, Crans-Montana, Switzerland.

Charlotte Niddam moved back to France after studying in Hertfordshire

“The families have asked that we all keep them in our thoughts and prayers during this extremely difficult time. We are all praying for a miracle for Charlotte and the others, and want the families to feel the full strength of the Immanuel College community’s support.”

A friend of Charlotte posted a video of them together, captioned: “My sweet sweet special Lottie I love you more than the meaning of life.”

Paolo Campolo, a Swiss-Italian financial analyst, said he had rescued ten people after his teenage daughter called to say her boyfriend and friends were trapped inside the bar.

Speaking from his hospital bed, where he is recovering from smoke inhalation, he told the Italian newspaper Il Messaggero: “There were several bodies all around. Alive but burnt. Some conscious, others not. They were begging for help in several languages. They were very young.”

Footage filmed by Ferdinand du Beaudiez, a French economics student, showed flames racing across the ceiling as people continued to sing and dance below. He managed to escape before returning inside in an effort to rescue his brother and girlfriend. They were both found outside.

A fire starting on the ceiling of a bar as people celebrate with sparkling champagne bottles.

Footage taken of the moment the ceiling ignited

He said he came across a badly burnt person lying on the stairs and he could not tell whether they were male or female. “Their clothes were gone,” he said. “I could only see their teeth.”

Letitia Brodard-Sitre, whose 16-year-old son Arthur is missing, said she had been waiting for news since the night of the fire. “I’ve been trying to get information ever since Wednesday night,” she told French and Swiss television. “He was in the bar with ten friends and they’re all missing. We haven’t been able to track them down in hospitals. I just need to know if he’s alive.

“I can’t bear the idea that my son might be lying somewhere hurt, without his mother, unable to answer his phone.

Arthur Brodard, 16, smiling while holding a package.

The death toll is expected to rise as up to 100 people are still in critical conditions. Many have been put into induced comas.

Stéphane Ganzer, head of security for the Valais canton, said: “Many of them have third-degree burns over more than 15 per cent of their bodies, and the risk of death remains even days after they were burnt.”

Other parents have made similar pleas on social media as the authorities work to identify victims. The first victim to be formally named was Emanuele Galeppini, 17, an Italian junior golfer. Swiss officials said that more identifications would take time because many bodies were badly burnt and required DNA or dental analysis.

Rory McIlroy, Emanuele Galeppini, and two other men smiling in a bar.

From left, golfers Luke Donald and Rory McIlroy, Emanuele Galeppini and former Manchester United striker Dwight Yorke

Mathias Reynard, president of the Valais canton, said officials understood the anguish of families but urged patience. “We are aware of the unbearable nature of the wait for the victims’ loved-ones as every hour, every minute passes … but unfortunately it takes time.”

Rescuers on scene at the site of a bar explosion in Crans-Montana.

Outside the bar

MAXIME SCHMID/AFP/GETTY IMAGES

A hospital in Sion initially received many of the injured, overwhelming its emergency services. Dozens were later transferred to specialist burns units in Switzerland and in France, Italy, Germany and Poland.

Mathias Reynard, Stephane Ganzer, and Frederic Gisler attending a press conference about a fire in a Swiss ski resort bar.

Mathias Reynard, Stéphane Ganzer and the commander of the Valais police, Frederic Gisler

ALESSANDRO DELLA VALLE/EPA

Eric Bonvin, the hospital’s director, said that doctors were racing against time. “Every minute counts,” he said. “At first, burns are not always visible. Nerve endings are destroyed and people may not feel the full extent of their injuries.” On Friday, about 30 patients remained at the Sion hospital in critical conditions.

Crans-Montana is a popular Alpine resort that attracts visitors from across Europe. Among the injured are people from at least nine countries, including 71 Swiss and 14 French citizens.

Witnesses describe the incident and the aftermath

No Britons are among the 113 injured whose identities have been confirmed, although six victims have yet to be formally identified.

Last night Yvette Cooper, the foreign secretary, wrote online: “As the Swiss emergency services continue to respond to the devastating tragedy in Crans-Montana, I have expressed our support to my counterpart, Ignazio Cassis.

Mourners gather at night to lay flowers and light candles to remember victims of a fire at Le Constellation bar and lounge.

Hundreds gathered for a vigil on Thursday night, including firefighters, below

ALESSANDRO DELLA VALLE/EPA

Firefighters at the scene of the Crans-Montana bar fire.

“Our thoughts are with all the victims and their families. The Foreign, Commonwealth and Development Office stands ready to support any British nationals affected.”