Jacques Moretti has been placed in pretrial detention for at least three months. He and his wife, Jessica Moretti, are under investigation over possible negligence.

Two people in blue and dark blue uniforms stand behind red and white striped barrier tape. One person's face is visible, the other wears a black balaclava.
The police on Jan. 2 outside Le Constellation bar in Crans-Montana, Switzerland, where a fire had swept through New Year’s celebrations.Credit…Sergey Ponomarev for The New York Times

A Swiss court on Monday ordered one of the two owners of a bar that caught fire during a New Year’s celebration to be placed in pretrial detention for at least three months, according to a court statement.

The owners, Jacques and Jessica Moretti, are under investigation over whether negligence played a role in the fire at Le Constellation bar in Crans-Montana, a popular ski town in the French-speaking part of Switzerland. The fire killed 40 people, most of them teenagers.

Investigators have said they believe the fire was started by sparklers but have not elaborated. Videos and witnesses have suggested that pyrotechnics placed on bottles of alcohol ignited the foam-covered ceiling of the bar’s basement.

Investigators interrogated the Morettis, a married couple who are both French citizens, on Friday in the nearby town of Sion.

The court, which under Swiss law had 48 hours to make a decision, approved a prosecutor’s request to place Mr. Moretti in pretrial detention “for an initial period of three months due to the risk of flight.” The court said that it could lift the detention order if other means were found to eliminate the flight risk.

It added that it was “not a question of punishing the defendant, who is presumed innocent until a possible conviction becomes final.”

Unlike her husband, Ms. Moretti was let go after questioning. The couple’s lawyers said in a statement that the decision would allow Mr. Moretti, “once the conditions are met, to regain his freedom.” The statement said that the couple would not “evade this legal process, which they will face together.”

Sébastien Fanti, a lawyer for three Swiss citizens injured in the fire, said that he and his clients were “not entirely satisfied” with the court’s decision to detain only Mr. Moretti. “This morning, the father of a child who was burned alive said to me, ‘He died as if in war, so now it’s war,’” Mr. Fanti said.