Valais public prosecutors have opened a criminal investigation into the operators of Le Constellation Bar in Crans Montana, Switzerland, after a fatal fire that broke out on New Years Eve.

Following the initial investigation conducted by the Valais public prosecutor’s office, a criminal investigation into negligent homicide and bodily harm and negligent causing of a conflagration was launched late Friday against the two operators of the bar, police said in a statement.

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The fire, which may have been caused by sparklers igniting the club’s soundproofing insulation, killed at least 40 people and left 119 injured. The injured, many of them teenagers, were moved to hospitals in neighboring countries for intensive care and treatment as Swiss hospitals operate at capacity.

The top priority at the moment is providing the best possible medical care and identifying the deceased, Swiss Justice Minister Beat Jans said at a press conference in Crans Montana on Saturday. Still, the question of responsibility is paramount, he added.

“The Federal Council has complete confidence in the law enforcement authorities,” he said, declining to comment further.

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The investigation examines all aspects of the incident, including the number of people allowed into the bar, accessible emergency exits, as well as renovation works done on the building and materials used, according to comments by chief prosecutor Beatrice Pilloud at a press conference Friday.

The bar in the Swiss ski resort of Crans Montana is owned by a French couple, according to multiple media reports. One of the pair, a woman, was in the bar and suffered burns to her arm but survived, while the man was elsewhere, French broadcaster BFMTV reported.