Sparklers and ceiling foam likely fuelled rapid spread of Swiss bar blaze

Investigators are probing why a New Year's Eve fire at Le Constellation bar in Crans-Montana spread so quickly, killing at least 40 people and injuring 119. Authorities said sparklers attached to champagne bottles that were held "too close to the ceiling" appear to have started the blaze in the bar's basement.

BBC Verify examined images and videos from the night showing people holding bottles with lit sparklers aloft and flames gathering on the ceiling. The team found no evidence the images had been manipulated using AI. Fire experts told BBC Verify the ceiling covering visible in footage resembles egg-box polyurethane acoustic foam, which can burn rapidly and produce dense toxic smoke if untreated or if fire-retardant coatings have degraded.

Officials said they cannot yet confirm the exact material or whether it met safety rules. Experts warned that ignition of such foam can trigger a flashover, when hot gases reach a critical temperature and a room ignites almost instantly, making survival unlikely. Investigators are also examining exit routes.

Video shows people scrambling up a narrow stairwell from the basement; officials said the building had multiple exits but could not confirm whether emergency doors were open. The canton’s fire-inspection authority normally oversees annual checks on buildings the size of the bar.

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AI, United States, World, Fire Safety, Switzerland, Nightclub, Investigation