Swiss officials now confirm that 40 people are dead and at least 119 are in hospital after a fire tore through a bar in Valais.
Attorney General Pilloud says the blaze appears to have been triggered by sparklers placed in champagne bottles and held too close to the ceiling, igniting the structure within seconds.
The rapid flash fire trapped many inside before they could escape.
Emergency services say several victims remain in critical condition, and the toll may still rise.
Investigators are examining whether safety rules were violated and if criminal charges will follow.
