Swiss prosecutors have agreed to Italy's request for a Joint Investigation Team (JIT) to be set up to probe the bar fire at the Swiss ski resort of Crans-Montana on New Year's Eve that killed 40 people, including six Italian teens, the Swiss Federal Office of Justice (FOJ) said on Tuesday.

The Italian ambassador to Switzerland Gian Lorenzo Cornado was recalled to Italy at the weekend after the Swiss authorities released the bar's co-owner, Jacques Moretti, from custody last week.

Premier Giorgia Meloni's office said Cornado would not return until a JIT was set up after she had a meeting with the ambassador on Monday.

"The Public Prosecutor's Office of the Canton of Valais has just informed the Federal Office of Justice (FOJ), in its function as the central authority for international mutual legal assistance in criminal matters, that by the end of the week it will comply with the Italian request," the FOJ said in a statement.