Switzerland will observe a national day of mourning on Friday with a memorial service honoring the 40 people killed earlier this month in a devastating fire at an Alpine bar during New Year’s celebrations.

The blaze broke out shortly before 2 a.m. on Jan. 1 at Le Constellation in the resort town of Crans-Montana, leaving 116 people injured, many of them seriously.

Investigators believe the fire was sparked by lit sparkling candles placed atop Champagne bottles, which ignited after coming too close to the ceiling. Authorities are examining whether ceiling soundproofing materials met safety regulations and whether the use of such candles was permitted inside the bar. Officials have also said the venue had not undergone a fire safety inspection since 2019.

The intensity of the flames and resulting burns made identification of some victims difficult, forcing families to provide DNA samples to assist authorities. Police said many of those killed were teenagers or young adults in their 20s.

Prosecutors in the Valais region have opened a criminal investigation into the bar’s two managers, who are suspected of involuntary homicide, involuntary bodily harm and involuntarily causing a fire.

As part of the nationwide remembrance, church bells across Switzerland will ring for five minutes beginning at 2 p.m. local time on Friday, followed by a minute of silence in memory of the victims.