Corinaldo, Italy - Six people, including five teenagers, died and dozens were injured in a stampede when panic broke out during a rap concert at an Italian nightclub early Saturday.
The suspected use of a pepper spray-like substance is thought to have sparked the chaos at the venue in the town of Corinaldo, near Ancona in central Italy.
"The cause may have been the dispersal of a stinging substance, the young people fled and trampled over each other. Sadly, six people died and dozens are injured," the fire service said in a statement on Twitter.
The victims include five people under the age of 18 - three girls and two boys - and an adult woman who accompanied her daughter to the concert.
Seven people are in a critical condition, doctors said, with at least 50 injured in total.
As the crowd panicked, people ran for the three emergency exits, one of which led to a small bridge and the car park.
The force of the fleeing crowd made a railing collapse and dozens of people fell, crushing those at the bottom of the pile, according to a preliminary investigation.
Grainy cellphone footage appeared to show part of a walkway collapsing, sending dozens of people tumbling down.
Ironically, those who remained inside the nightclub were unharmed.
"We were dancing and waiting for the concert to start when we smelt this pungent odour," a 16-year-old boy who was taken to hospital told the media.
"We ran to one of the emergency exits but we found it blocked, the bouncers told us to go back."
A pile of abandoned shoes testified to the chaos of the stampede, with survivors and the bereaved weeping outside the nightclub as emergency vehicles tended to the injured, local newspaper Ancona Today reported.
"It can't be! You can't die like that. Wake up Mattia, I beg you," one unnamed woman cried as she knelt by her son's body, the paper said.
Around 1 000 people - many of them young - were in the Lanterna Azzurra (Blue Lantern) club for a performance by Italian rapper Sfera Ebbasta, known as "the king of the trap" for his style of Hip Hop.
"I'm deeply saddened by what happened," Ebbasta said on Instagram.
"I don't want to pass judgement on who is responsible, but I would just like to ask everyone to stop and think how dangerous and stupid it can be to use pepper spray in a nightclub," he said, cancelling all his upcoming promotional events.
Pope Francis said during Saturday's Angelus prayers that he would pray for "the children and the mother who died last night... as well as for the injured."
The Ancona public prosecutor and police are trying to establish how many people were in the venue at the time of the stampede, with media reporting many more people inside than the authorised maximum of 871.
The injured were taken to hospital in the nearby town of Senigallia and the most serious on to Ancona.
"You can't die like this at 15," said far-right Interior Minister Matteo Salvini, promising to "find those responsible for these six broken lives, those who through wickedness, stupidity or greed turned a festive evening into a tragedy."
His anti-immigrant League party was to hold a minute's silence during a previously planned rally in Rome on Saturday morning.