It was the moment New Year’s revelry turned into catastrophe.

A photo shows partygoers hoisting wine bottles fitted with sparklers, yet even as they toast the occasion flames are already visible on the foam soundproofing lining the low ceiling of the bar at the upscale Alpine ski resort.

The fire, which broke out around 1:30 a.m. (7:30 p.m. ET Wednesday) at Le Constellation bar in Crans-Montana, Switzerland and left 40 dead, appears to have started when sparklers atop bottles were brought too close to the ceiling, Beatrice Pilloud, the Valais canton Attorney General, told a news conference Friday after preliminary investigations.

The sparklers appear to have led to “what is referred to as a flashover incident where the fire spread very rapidly,” she said. Investigators would assess soundproofing foam used in the ceiling, and whether anyone needs to be held criminally liable for the fire, she added.

On Friday, officials set about the painful task of identifying the dozens of charred bodies left by the fire, while emerging images and eyewitnesses gave an indication of the horrific scene that unfolded.

One video — like that photo, geolocated by NBC News to inside the venue in the early hours of New Year's Day — suggests that the panic was not immediate. Even as flames licked the rafters and debris began to drip down, some onlookers filmed on their phones while others kept dancing or talking over the music. Another person attempted to beat the flames with a white T-shirt.

Soon, it became clear this was a grave emergency. Another video shows the fire more advanced, the person filming quickly turning to run up the stairs toward the exit, urging others to hurry or get out of the way.

The official death toll still stands at 40, officials said on Friday.

Of the 119 people injured, 71 were Swiss nationals, 14 were French, 11 Italian, four Serbian, and one each from Bosnia, Belgium, Luxembourg, Poland and Portugal, Mathias Reynard, head of the regional government of the Valais canton, told Friday’s news conference. The nationality is unknown for 14 of those injured.

On Thursday evening, mourners had arranged hundreds of candles at a traffic circle near the venue, which had by this point been covered up in white plastic by authorities. There was an air of somber stillness, with the mostly young crowd sharing hugs, and expressions of shock and disbelief.

Swiss President Guy Parmelin described it Thursday as “one of the worst tragedies that our country has experienced.”