SKOPJE, North Macedonia — A massive fire that broke out early Sunday in a nightclub in North Macedonia’s eastern town of Kocani has killed 51 people and injured about 100 more, interior minister Panche Toshkovski told a press conference.

The blaze began around 2:35 a.m. during a concert by a local pop group, according to Toshkovski. He said the young clubgoers used pyrotechnics that caused the roof to catch fire. Videos showed chaos inside the night club, with young people running through the smoke as the musicians urged people to escape as quickly as possible.

“This is a difficult and very sad day for Macedonia. The loss of so many young lives is irreparable, and the pain of the families, loved ones and friends is immeasurable,” North Macedonia’s prime minister, Hristijan Mickoski. wrote on X, formerly Twitter.

“The people and the government will do everything in their power to at least slightly alleviate their pain and help them in these most difficult moments.”

Family members have gathered in front of hospitals and Kocani’s city offices begging authorities for more information.

Toshkovski said police have arrested one man, but didn’t provide details on the person’s involvement.