Authorities confirmed on Friday that the cause of the deadly nightclub fire in the Swiss Alps that left 40 dead and another 100 injured were from sparklers that were held too close to the ceiling.

Valais attorney general, Beatrice Pilloud said that investigators “are pursuing several hypotheses” and that “no scenario is being ruled out”.

“We currently assume that the fire was caused by sparklers attached to champagne bottles that came too close to the ceiling,” she said according to a report from BBC News. “This caused the fire to spread quickly. Initial evidence has been secured at the scene.”

Officials had originally refused to confirm rumors that it was sparklers or birthday candles that had ignited foam material attached to the low ceiling of the basement room at Le Constellation in the ski town of Crans-Montana. On Thursday they said the cause of the blaze — initially reported as an explosion — was under investigation, though authorities said early evidence suggests it was an accident rather than an attack. 

Two French women who said they were inside the bar told France’s BFM TV that the fire began in the basement after a bottle containing “birthday candles” was held too close to the wooden ceiling.

“The fire spread across the ceiling super quickly,” one of the women, who identified themselves as Emma and Albane, told the French news agency. The pair said they managed to climb a narrow staircase to the ground floor and escape.

Another club goer said that he had arrived to the crowded La Constellation shortly after midnight on Thursday and saw young people dancing to pop music in the basement area of the club, with waiters scurrying across the dance floor with wine bottles topped with candles. Suddenly the ceiling was on fire and the room was engulfed within minutes.

“I saw my hands decomposing,” 20-year-old Noa Bersier said to the New York Times. “I felt like I was on fire. But there was no fire around me.”

Amid a melee of people trying to escape the growing fire, he made it to a veranda at the top of the stairs but did not avoid injury.

“You see panic in everyone’s eyes. There are screams, we’re burning, we see our skin decomposing,” he said. “That’s when I saw my hands, the skin hanging off on all sides.”

“My face was half-burned, I could tell that my hair was burned. I stank of burns.”

Friends then drove Mr. Bersier to a nearby hospital where he was treated for burns on his head, hands, lower back, and leg.

“I’m really grateful to still be here today,” he said, “compared with others who couldn’t make it.”

Eyewitnesses described a harrowing scene on the streets as club revelers escaped from the burning club.

“I didn’t see the fire, but I saw all the bodies on the streets … They were with white sheets over them, these people were dead already, and then you saw the young people, because it’s all young people,” Edmund Coquette told RTL Germany. “You saw the young people who were totally burned in the face, who missed some fingers, laying on the streets.”

Head of the Swiss Judicial Police, Pierre-Antoine Lengen, said that the “absolute priority” was identifying the victims, but that it could take several days before all bodies are accounted for.