(CNN) A stampede at a rap concert early Saturday in an Italian nightclub killed five teenagers and one adult, and left dozens of people injured, authorities said.
About 100 were treated for injuries after the chaos at the Lanterna Azzurra nightclub in Corinaldo, authorities said.
Hundreds had been waiting to see popular rapper Sfera Ebbasta perform when someone in the club sprayed an "irritant substance," leading to a stampede, Italy's civil protection agency said.
As people rushed out, a metal fence collapsed outside the club, causing some to fall "one on top of the other" and leading to the deaths and injuries, said Luca Cari, spokesman for firefighters in Ancona province on Italy's eastern coast.
Those fleeing the club probably were alarmed by a strong smell of pepper spray, Cari said.
Five teens and a woman who had accompanied her daughter to the concert were killed, said Luigi Di Maio, a deputy prime minister. He identified the dead as Asia Nasoni, 14; Daniele Pongetti, 16; Benedetta Vitali, 15; Mattia Orlandi, 15; Emma Fabini, 14; and Eleonora Girolimini, 39.
"These (victims) are young people. It's absurd to die this way. As a government we will do everything we can to clarify the circumstances and make sure the security norms were followed," Di Maio posted on Facebook.
Paramedics were seen helping concertgoers on the street following the stampede.
Thirty-five of about 100 people who were treated remained in a hospital Saturday afternoon, including seven whose conditions were life-threatening and another five in serious condition, said Oreste Capocasa, chief of police in Ancona.
Italian Interior Minister Matteo Salvini, who also is a deputy prime minister, held a moment of silence in honor of the victims during a political rally in Rome.
"You cannot die like this at 15. Thoughts and prayers for the six dead tonight in Marche. I hope (those) who are seriously injured in the hospital get well. And a commitment: find the responsible," Salvini tweeted hours after the stampede.
Italian President Sergio Mattarella promised to work tirelessly to determine "any responsibility and negligence."
"Citizens have the right to feel safe everywhere, in workplaces and in leisure areas. Therefore, safety must be assured with particular care in crowded meeting places, through rigorous controls," Mattarella said in a statement. "No one should die this way."
Sfera Ebbasta, in a post on Instagram, said he was deeply saddened by what happened.
"It's difficult to find the words to express the regret and sadness of these tragedies," the rapper wrote in Italian, according to a CNN translation.
He said he would cancel his promotional events over the coming days out of respect for the dead and injured.
Corinaldo is 145 kilometers (about 90 miles) east of Florence.