What images and videos tell us about why Swiss bar fire spread so quickly

Investigators are examining the New Year's Eve fire at Le Constellation bar in Crans-Montana, Switzerland, that killed at least 40 people. Authorities believe sparklers attached to champagne bottles held too close to the ceiling ignited the blaze. BBC Verify analyzed videos and images from the scene, confirming their authenticity and timeline, which show people holding bottles with sparklers aloft, with flames appearing on the ceiling. A key focus is how the fire spread so rapidly and the bar's safety record. Investigators are also examining foam-like padding on the ceiling to determine if it met safety standards, with experts identifying it as potentially flammable polyurethane.