The detention was ordered due to concerns over flight risk, as investigators intensify a criminal probe into the tragedy.

The blaze broke out at the Le Constellation bar during a crowded holiday celebration, shocking Switzerland and neighbouring countries.

Authorities are investigating the French owners on suspicion of homicide by negligence and other serious criminal offences.

Local media reported that Jacques Moretti, one of the bar’s co-owners, was remanded in custody following questioning by prosecutors in the canton of Valais.

Under Swiss law, a court must decide within 48 hours whether continued detention is legally justified.

Moretti and his wife Jessica were summoned for a hearing at the public prosecutor’s office in the town of Sion earlier on Friday.

Video footage later showed Jessica Moretti leaving the building alone, while her husband remained in custody.

In a brief statement, Jessica Moretti expressed sorrow for the victims and apologised to those affected by the tragedy.

She said her thoughts remained with the injured and grieving families as investigations continue.

Swiss authorities declared Friday a national day of mourning to honour those who lost their lives in the inferno.

Church bells rang across the country as communities paused to remember the victims.

More than half of the deceased were teenagers, turning the incident into one of Switzerland’s deadliest nightclub disasters.

At least 116 people were injured, many suffering severe burns and smoke inhalation.

The tragedy drew international attention as several French and Italian citizens were among the dead.

Italian Prime Minister Giorgia Meloni called for strict punishment for those responsible for the fire.

French President Emmanuel Macron and Italian President Sergio Mattarella joined Swiss leaders at a memorial in Martigny.

Firefighters, victims’ families and officials observed a minute’s silence and laid white roses in tribute.

Dozens of mourners also gathered near the closed bar in Crans-Montana despite heavy snowfall.

Flowers, letters and teddy bears were placed beneath a protective igloo built to shield the memorial items.

Investigators believe the fire may have been triggered by sparkling candles used inside the venue.

Witnesses said the candles ignited foam soundproofing on the basement ceiling, causing flames to spread rapidly.

Serious questions have been raised about safety oversight at the bar.

The local mayor admitted the establishment had missed several mandatory safety inspections.

Swiss President Guy Parmelin said those responsible must be held accountable without delay or leniency.

Regional leader Mathias Reynard added that political authorities must also answer for any failures.

Prosecutors previously stated that legal grounds for detention had not initially been met.

New findings and concerns over possible evasion appear to have changed that assessment.

Families of the victims have filed legal complaints seeking justice and accountability.

International cooperation is expected as multiple nationalities were affected by the disaster.