The blaze began at about 1:30 a.m. local time in the crowded venue in the canton of Valais. Swiss authorities said they were treating it as an accidental fire rather than an attack. Prosecutors opened an investigation into its origin and the speed with which flames and smoke spread through the bar.
Officials said sparklers fixed to champagne bottles and held close to the ceiling appeared to be the likely ignition source, although they stressed that several hypotheses remained under review. Witnesses described seeing a lit bottle near ceiling material before the fire expanded rapidly. Video and witness accounts also depicted people rushing to escape, some breaking windows as they fled. Investigators were examining the building’s layout, exits and safety record rather than treating the early explanation as a final finding.
The casualty response stretched across Switzerland. Patients were transferred to hospitals in Sion, Lausanne, Geneva and Zurich. Lausanne University Hospital was treating 22 injured people between the ages of 16 and 26; eight had required resuscitation on arrival before entering critical and specialist care. Medical staff warned that treatment for severe injuries could continue for weeks or months.
Of the 119 injured, authorities had formally identified 113 within the first days. That group included 71 Swiss citizens, 14 French citizens and 11 Italians, reflecting the international clientele of the resort. Identification of those killed proceeded more slowly because of the severity of burns. Officials established a reception centre and helpline for families, while schools, sports clubs and relatives circulated information about missing teenagers.
Le Constellation occupied two levels, with a main-floor bar and a basement club reached by stairs. The establishment was popular with tourists and younger visitors. Crans-Montana itself has about 10,000 residents and is an internationally known ski destination, increasing the likelihood that victims came from several countries.
One of the venue’s owners told Swiss media that the bar had undergone three inspections over 10 years and said its operators would cooperate with the investigation. That statement was not an official safety finding. Forensic teams worked behind police tents surrounding the site as mourners left flowers nearby.
The inquiry therefore centred on two connected questions: what ignited the ceiling and why the fire became so deadly so quickly. While officials had identified bottle sparklers as the leading theory, the definitive cause, compliance history and evacuation conditions remained matters for investigators.
