Fifty-one people were killed and more than 100 injured when a fire broke out in a nightclub early on Sunday in the North Macedonian town of Kocani, Interior Minister Pance Toskovski said.

The fire was caused by “pyrotechnic devices” used during a concert, Toskovski said.

“Sparks caused fire … and fire spread through the discotheque,” he said.

A video from the event, verified by Reuters, shows a band playing on stage flanked by two flares firing white sparks into the air. The sparks set the ceiling alight above the band, who appear to step away as the video cuts.

Firefighters doused the charred and smoking entrance to the club, named ‘Pulse,’ TV footage from a local broadcaster showed.

North Macedonia’s MRT public broadcaster reported that 27 people were hospitalized at the Skopje City Hospital with severe burns, and another 23 were being treated at the Clinical Center. Among the injured were minors, it said.

The blaze broke out at 3:00 am in Kocani.

Prime Minister Hristijan Mickoski said in a post on Facebook: “This is a difficult and very sad day for Macedonia! The loss of so many young lives is irreparable, the pain of the families, loved ones and friends is immeasurable.”

“I call on all competent institutions – health services, relevant authorities – to take urgent measures to assist the injured and support the families of the families.”