Dozens of people were killed in a fire at a nightclub in North Macedonia’s southern city of Kocani, local authorities said Sunday.

At least 59 people — all aged 18 to 23 — were killed, Panche Toshkovski, North Macedonian minister of interior, said during a news conference on Sunday. Among the victims was a police officer, who was in the Club Pulse nightclub on duty, Toshkovski said.

Dr. Kristina Serafimova, the head of the Kocani General Hospital, told ABC News that those who perished were killed by smoke inhalation, burns and a stampede triggered by the fire. Serafimova said there was only one exit from the nightclub in Strumica.

Another 155 people were injured in the incident, all of whom are aged between 14 and 24, Serafimova and Toshkovski said. Around 10 of those injured are in critical condition and on respirators fighting for their lives, Serafimova said.

The most serious cases have all been transferred to hospitals in other parts of the country or abroad, Serafimova said.

Arrest warrants have been issued for four people, said Toshkovski, who declined to provide further information. Authorities are investigating the cause of the fire and possible safety violations.

Toshkovski said the Ministry of Economy and Public Prosecutor’s Office are collecting documents related to the nightclub and those alleged to have been responsible for the tragedy.

A switchboard operator at one of the hospitals treating victims told ABC News, “It’s a catastrophic tragedy.”

The manager of the band DNK, which was performing at the Pulse nightclub when the fire broke out, told ABC News that the venue had a maximum capacity of 500 to 700 people.

The band, which consists of eight members, was performing at the time of the fire and some of them were among the injured, the manager said.

The mayor of Strumica, Konstantin Kostantinov, told ABC News that the 24-year-old drummer for DNK is among those who died in the nightclub fire.

Kostantinov also expressed condolences and support for families who lost loved ones, adding that the whole of North Macedonia is in shock and mourning over this tragedy.

Pope Francis, who remains hospitalized in Rome for treatment, sent a telegram to Bishop Kiro Stojanov in Skopje, North Macedonia, expressing his condolences, according to the Vatican.

In the telegram, which was signed by Cardinal Pietro Parolin, the Vatican secretary of state, the pope said he is praying “for those who lost their lives” and for their loved ones.

As more details of the incident emerged, the families of the young people who attended the concert — some of them underage — appealed for information on social media, sharing phone numbers and personal details in the hope that those still missing can be found.

Serafimova told ABC News that only around half of the victims were carrying identification. Family members of the missing have been asked to come to Kocani hospital to help identify their loved ones, she added.

The blaze began around 2:35 a.m. local time, according to Interior Minister Toshkovski, who said the venue’s roof was set on fire by pyrotechnics used by clubbers.

Toshkovski said police arrested one man, but did not give any further details.

North Macedonian Prime Minister Hristijan Mickoski wrote on X, “The loss of so many young lives is irreparable, and the pain of the families, loved ones and friends is immeasurable.”

“The government is fully mobilized and will do everything necessary to deal with the consequences and determine the causes of this tragedy,” Mickoski added. “In these times of deep sadness, when our hearts are broken with pain due to this terrible tragedy, I call for unity, solidarity, humanity and responsibility.”

Among those offering condolences from abroad was Ukrainian President Volodymyr Zelenskyy. “I wish those who were injured a speedy recovery,” he wrote in a post to X. “Ukraine mourns alongside our [North] Macedonian friends on this sad day.”

Albanian Prime Minister Edi Rama said his nation was ready “to provide any assistance that may be needed.”

European Commissioner for Enlargement Marta Kos said on X that she was “deeply saddened” by the “terrible tragedy.”