Switzerland will hold five days of mourning after an “unprecedented” fire tore through a crowded bar, killing about 40 people and injuring 115 who were celebrating at a New Year’s Eve party in the Alpine ski resort of Crans-Montana.

Axar.az informs, citing Guardian, the country’s president, Guy Parmelin, described the blaze as one of the most traumatic events in Switzerland’s history. “It was a drama of an unknown scale,” he said, paying tribute to the many “young lives that were lost and interrupted”.

Witnesses said the fire broke out at 1.30am in the town’s Le Constellation bar after sparklers or flares were put into champagne bottles. Two women told the French broadcaster BFMTV a bartender carried a female member of staff who was holding one of the bottles.

The flames set fire to the ceiling. Within seconds the blaze had spread, engulfing a crowded basement packed with revellers. Many were teenagers. One of the women described a crowd surge as people desperately tried to escape up a narrow flight of stairs.