(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.

Forensic teams and police cordon off the Lanterna Azzurra club's entrance Saturday in Corinaldo.

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.

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