All 116 people injured in the fire that tore through a bar in the Swiss ski resort of Crans-Montana on New Year’s Eve, killing 40 mostly young partygoers, have been identified, police have said, as the bodies of the first foreign victims were repatriated.

Police in Valais canton said in a statement on Monday they had revised the number of wounded down from 119 because three people admitted to accident and emergency wards on Thursday morning had been wrongly recorded as injured in the blaze.

Authorities believe the fire in the crowded Le Constellation bar started in the basement after sparklers attached to champagne bottles were held too close to the ceiling, which images on social media suggest was clad with soundproofing foam.

Among the injured were 68 Swiss citizens, 21 French, 10 Italians, four Serbs and four dual nationals, police said, as well as two Poles and one person each from seven other countries. Eighty-three people were still in hospital being treated for severe burns.

The last of the 40 people who died in the fire – who included 21 Swiss nationals, nine French citizens including two with dual nationality, six Italians, and one person each from Belgium, Portugal, Romania and Turkey – were identified on Sunday.

Authorities have not yet released the names of the victims, although several have been publicly identified by their families. They were between 14 and 39 years old, but were overwhelmingly young: 20 were minors, and the average age was 19.

The bodies of five of the six dead Italian nationals were being repatriated on Monday. Four Swiss police officers carried each coffin on to an Italian transport plane in the military area of Sion airport, about 16 miles (25km) from Crans-Montana.

The plane was due to land at Milan airport late on Monday, where the bodies of Achille Barosi and Chiara Costanzo from Milan, Giovanni Tamburi from Bologna and Emanuele Galeppini from Genoa would be received by officials and relatives.

It would then fly on to Rome with the coffin containing the body of Riccardo Minghetti, the Italian government said. The sixth Italian victim, Sofia Prosperi, lived in Switzerland and would be buried there.

“We have pledged to do everything we can, in conjunction with Swiss authorities,” said Gian Lorenzo Cornado, Italy’s ambassador to Switzerland. “We will follow the investigation closely so the truth is known as quickly as possible and justice served.”

Pressure was mounting for answers about how the tragedy could have happened. Authorities are investigating the bar’s owners, French nationals Jacques and Jessica Moretti, on suspicion of crimes including homicide by negligence.

The married couple have not so far been placed under arrest and are not seen as a flight risk, the public prosecutor has said. But the Swiss tabloid Blick on Monday demanded to know “why the couple running the bar are still free”.

In a social media post, Italy’s far-right deputy prime minister, Matteo Salvini, said there had been a failure to ensure the bar’s basement was safe, adding that “in civilised Switzerland, the prison gates will have to open for quite a few people”.

Tages-Anzeiger, another Swiss newspaper, said questions remained to answered about age checks at the bar, the soundproofing material used in the basement and the standards governing the use of the sparklers, so called “Bengal fountains”.

Jacques Moretti has said Le Constellation had been checked three times in 10 years and that everything had been done according to the rules, and local officials in Crans-Montana have said no concerns had been raised or defects reported.

The municipality has given investigators all documents relevant to the investigation and joined the criminal proceedings as a civil party. “This will allow [the town council] to actively contribute to establishing all the facts,” it said.

The town will hold a memorial ceremony on Friday honouring the victims. The French government said on Monday that President Emmanuel Macron would attend.

Reuters and Agence France-Presse contributed reporting