Jacques Moretti, co-owner of the Swiss bar which went up in flames during New Year celebrations, was being held in custody after being interviewed by prosecutors on Friday, a source told AFP.

Moretti and his wife Jessica, who co-own Le Constellation bar in the ski-resort of Crans-Montana, were interviewed by prosecutors in the Switzerland's southwestern Wallis canton, as the country held a national day of mourning for the 40 people killed in last week's disaster. The average age of those killed was 19.