Jacques Moretti was first detained on Friday for an initial period of 48 hours.
On Monday, a judge at what is known as a court of coercive measures ruled that he should be kept in custody for three months – a period that can be renewed under Swiss law.
It is known as provisional – or preventive – detention and is meant to last until a case goes to court.
In this instance, the court said the measure may be lifted upon payment of bail, whose sum would be set later.
The couple were placed under criminal investigation days after the devastating fire.
Moretti’s wife, Jessica, who is under house arrest, told reporters on Friday that she was sorry about the “unthinkable tragedy”.
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.
