A fire that tore through a bar at a Swiss ski resort killing at least 40 people likely started when "fountain candle" sparklers were held aloft too close to the ceiling, the region's chief prosecutor said on Friday.
Investigators are combing through the blackened ruins of the venue, examining videos on social media and interviewing survivors for clues on how the fire began in the early hours of New Year's Day in the bar's basement and spread so fast.
Witnesses have recounted seeing bar staff carrying sparkling fountain candles attached to bottles of champagne. The Valais canton's chief prosecutor, Beatrice Pilloud, said the sparklers were a leading line of enquiry that looked to be firming up.
"Everything suggests that the fire started from the burning sparklers ... that had been attached to champagne bottles and were moved too close to the ceiling," Pilloud told a news conference. "From there, a rapid, very rapid and widespread blaze ensued."
However investigators are pursuing several hypotheses and no scenario has been ruled out, she added.
Thorough investigation of the venue is underway
The probe will also focus on previous renovations at the Constellation bar and the materials used, the availability of adequate fire extinguishing systems and escape routes, and the number of people who were in the bar when the fire started.
Pilloud said the investigators were examining acoustic-dampening foam in the ceiling of the basement to assess whether it complied with regulations, whether its installation was authorised, and what role it played in the fire's rapid spread.
The probe will determine if annual building inspections had been carried out at the required intervals, but the town had not raised concerns or reported defects to the canton, Stephane Gazner, head of security in Valais, told the news conference.
Investigators have interviewed the bar's owners, a French couple who bought the bar in the Crans-Montana resort in 2015 according to the Valais company registry.
Asked if the pair had been instructed not to leave Switzerland, Pilloud said they had not been interviewed under caution, but added: "If there is a flight risk, it is possible for us to take the measures needed."
Further investigations will determine whether there are grounds for criminal liability involving any individuals, Pilloud added.
"If this is indeed the case and these individuals are still alive, an investigation will be opened against them for negligent arson, negligent homicide, and negligent bodily injury," the prosecutor said.