Italy has recalled its ambassador to Switzerland for consultations after Swiss authorities released the owner of a nightclub where a New Year’s Day fire killed 40 people — a move Rome condemned as a “grave offense” and a fresh wound for victims’ families.

Italian Prime Minister Giorgia Meloni and Foreign Minister Antonio Tajani ordered Ambassador Gian Lorenzo Cornado to return to Rome and instructed him to formally protest the decision with prosecutors in the Swiss canton of Valais, citing the seriousness of the alleged crimes, the risk of flight and concerns over possible evidence tampering, according to media reports.

Rome said in a statement on Saturday that it is seeking “truth and justice” for the victims, several of whom were Italian nationals.

The diplomatic escalation follows the Jan. 1 fire at Le Constellation nightclub in the Swiss resort of Crans-Montana, which broke out during New Year celebrations shortly after 1 a.m., killing 40 people and injuring 116.

Investigators believe indoor pyrotechnic sparklers attached to champagne bottles ignited flammable acoustic foam on the ceiling, triggering a rapid flashover that engulfed the packed basement venue within seconds.

Swiss prosecutors opened a criminal investigation into the bar’s owners on suspicion of negligent homicide, bodily harm and arson.

Jacques Moretti, one of the bar’s co-owners, had been detained earlier this month as a flight risk before a Swiss court ordered his release on bail on Friday.