Did fireworks on champagne bottles trigger deadly blaze in Swiss ski resort bar?

A fire at Le Constellation bar in Crans-Montana, Switzerland on New Year's Eve killed 47 people and injured over 100, many of them young. Authorities are investigating the cause, with theories including firecrackers, birthday candles on champagne bottles, or pyrotechnics, but no sign of terrorism. Switzerland declared five days of mourning; international leaders expressed condolences as identification of victims continues.