Firefighters took more than an hour to control huge flames that broke out on the top floor of a four-story residential building in the densely populated Jabalia refugee camp in the northern Gaza Strip. Witnesses said they heard screams but were unable to help those inside due to the intensity of the fire. Ambulances rushed several wounded to local hospitals and Israel, which along with Egypt maintains a blockade on Gaza, said it would allow those in need of medical treatment. Gaza’s interior ministry said an initial investigation revealed large quantities of gasoline had been stored at the site, sparking the fire, which quickly engulfed the building. Gaza, ruled by Hamas and under a crippling Israeli-Egyptian blockade, faces a severe energy crisis. People often store cooking gas, diesel and petrol in homes to prepare for winter. House fires have been caused by candles and gas leaks in the past. Palestinian President Mahmoud Abbas called the incident a national tragedy and said a day of mourning would be declared. 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 transport serious cases to be treated outside the pouch. it it’s necessary. “The president has directed to urgently provide all forms of medical and other assistance,” Sheikh tweeted. Tor Wennesland, the UN envoy for peace in the Middle East, expressed his “sincere condolences” to the families of those who lost their lives in the incident, in a post on Twitter. 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.