Investigators are probing the rapid spread of a deadly fire at Le Constellation bar in Crans-Montana, Switzerland, which killed at least 40 and injured 119. The fire is believed to have started from sparklers on champagne bottles held too close to the ceiling. Concerns are raised about the bar's safety record, including the type of foam padding on the ceiling. Experts warn that untreated polyurethane foam can be highly flammable, contributing to rapid fire growth. Authorities are also examining exit routes and past safety inspections.