Six people died after a stampede in a Nightclub in Corinaldo on Saturday morning, with the five of the deceased confirmed to be teenagers.
Some survivors were quoted by Italian media as saying at least one fire exit was blocked when concertgoers tried to get out. About 50 other people were injured, about a dozen seriously.
"The cause may have been the dispersal of a stinging substance, the young people fled and trampled over each other", firefighters said on Twitter.
One of dead was a mother of a teenager.
Paramilitary police are investigating the cause, in addition to fire officials.
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The Lanterna Azzurra club was hosting a concert by rapper Sfera Ebbasta and up to 1,000 people were thought to be inside.
It was not immediately clear how many people were inside the club when the stampede erupted or what the venue's maximum capacity is. But Salvini said initial investigation "appears to knock down that possibility".
Poggiali said he didn't have any immediate confirmation from survivors that the use of an irritating spray, like pepper spray, had set off the panic.
Salvini vowed that responsibility would be determined for the "six broken lives - whoever out of nastiness, stupidity or greed transformed an evening of partying into tragedy".
The incident occurred at a disco in Corinaldo, where an Italian rapper was entertaining the crowd, police chief Oreste Capocasa said in nearby Ancona.