One of the two co-owners of the Swiss bar where 40 people died in a fire on New Year’s Eve has been detained.

Swiss prosecutors said Jacques Moretti, a French national, was a potential flight risk. He and his wife Jessica, who is also French, are suspected of manslaughter by negligence, bodily harm by negligence and arson by negligence.

The blaze at Le Constellation bar in Crans-Montana left 116 people injured. Many of the victims were aged under 20. The fire is believed to have been started by sparklers in champagne bottles raised too close to the ceiling during celebrations.

It emerged this week that the bar in the popular ski resort had not undergone safety checks for five years.

The decision to detain Jacques Moretti came after he and his wife, Jessica, who own the bar together, were on Friday questioned by prosecutors in Sion, a town in the canton of Valais.

Under Swiss law, the subject of an investigation is kept in custody until a court decision is made within 48 hours.

The couple had been earlier placed under criminal investigation.

On Friday, Jessica Moretti told reporters: “My constant thoughts go to the victims and those who are fighting today.

“This was an unthinkable tragedy and never could we have imagined this. It happened in our bar and I want to say I’m sorry,” she added as she walked through the streets of Sion surrounded by police.

The co-owners had earlier said they were “devastated”, pledging “full co-operation” with the ongoing investigation.

The prosecutors have said they believe the fire started when people celebrating the New Year raised champagne bottles with sparklers attached, setting light to sound-insulating foam on the ceiling of the basement bar.

On Friday, Switzerland staged a minute’s silence on a national day of mourning for the victims of the fire.

Church bells then rang across the country for five minutes.

Trains and trams came to a halt and Zurich airport briefly paused operations.

At a local commemoration staged in Crans-Montana, there was a standing ovation for firefighters.

The news that the bar had not been inspected for five years has shocked families of the victims.

Romain Jordan, who represents some of the families, said earlier this week the “staggering number of breaches and shortcomings in the inspections raises the question of whether the municipality should be investigated with even greater urgency”.

Venues like Le Constellation should have been checked annually, but Crans-Montana Mayor Nicolas Feraud said on Tuesday he could not explain why this had not been done for so long at that bar.

“We regret that – we owe it to the families and we will accept the responsibility,” he said.

He added that sparklers would be banned in local venues.

Most of the victims of the fire were young – eight were under the age of 16.

Many of the injured have severe burns and are being treated in Switzerland and other European countries.

The funerals of some of those who died have been taking place.