At least 21 people were killed and several others injured after a fire broke out in a residential building in the densely populated Jabalia refugee camp in the northern Gaza Strip, local sources said. Ambulances rushed several wounded to local hospitals and Israel, which along with Egypt maintains a blockade on Gaza, said on Thursday it would allow those in need of medical treatment. Palestinian news agency WAFA reported that several children were among the dead. Gaza’s interior ministry said an initial investigation revealed large quantities of gasoline had been stored at the site, sparking the fire that quickly engulfed the building. Firefighters took more than an hour to control the huge flames that broke out on the top floor of a four-story residential building. Witnesses said they could hear screams but were unable to help those trapped inside due to the intensity of the fire. Hamas, which rules Gaza, said an investigation was underway to determine the cause of the fire. [Mahmud Hams/AFP] Hamas, which rules Gaza, said an investigation was underway to determine the cause of the fire. “It is a tragic incident. Many of the victims have not yet been identified as they have been badly burned,” said Al Jazeera correspondent Youmna ElSayed, reporting from Gaza. He said candles lit during a birthday party caused the fire. “When the candles were lit, a fire quickly broke out and there was an explosion,” he said. Civil defense agencies in the city are ill-equipped to deal effectively with such emergencies, Al Jazeera’s ElSayed said. Palestinian President Mahmoud Abbas called it a national tragedy and said there would be a day of mourning. Hussein al-Sheikh, secretary general of the Palestine Liberation Organization (PLO) executive committee, said in a statement that the Palestinian Authority urged Israel to open the Erez crossing with Gaza to bring in serious cases to deal with outside of the besieged enclave if necessary. Deeply saddened by the tragic death of 21 people after a fire broke out in the Jabalia refugee camp, north of #Gaza. According to information, among the dead are at least 8 children, 4 women and 1 retired UNRWA employee. Our deepest condolences go out to the families and community — UNRWA (@UNRWA) November 17, 2022 Jabalia is one of eight refugee camps in Gaza, home to 2.3 million people and one of the most densely populated areas in the world. The enclave has been under an air, sea and land blockade imposed by Israel since 2007. “The President has instructed the urgent provision of all forms of medical and other assistance,” al-Sheikh said on Twitter. A spokesman for COGAT, the Israeli Defense Ministry unit that manages the Erez crossing, told AFP that Israel “will provide assistance … as needed” through the crossing point. UNRWA, the United Nations agency for Palestine refugees, tweeted that it was “deeply saddened by the tragic loss of 21 people” in the fire and expressed its “deepest condolences to the families and community”. Tor Wennesland, the UN envoy for peace in the Middle East, also expressed his “sincere condolences” to the families of those who lost their lives in the incident, in a post on Twitter. Palestinian firefighters at the building in the Jabalia refugee camp [Mahmud Hams/AFP]