At least 20 people were killed and several injured after a fire was ignited in the northern Gaza Strip, health authorities said Thursday.

What do we know so far?

The blaze broke at the Jabalila refugee camp after residents participated in a party.

Indonesian hospital head Salah Abu Laila confirmed that 20 bodies had been "burned" by the fire. 

Palestinian news agency Maan reported that many of the victims were from one family.  

Witnesses at the scene heard victims pleading for help, but were unable to rescue them due to the intensity of the flames. 

Palestinian news agency Wafa reported that Palestinian Mahmoud Abbas had declared a national day of mourning on Friday following the catastrophe. 

Investigation underway 

The Hamas-run Civil Defense in Gaza said the fire was ignited by gasoline that was being kept in the building. A probe into the incident is currently underway. 

Amid an Israeli blockade that limits materials into the strip, many Gazans store gasoline and diesel in their homes ahead of winter. 

Senior Palestinian Authority official Hussein al-Sheikh urged Israel to open the Erez border crossing following the incident, so injured people can receive help at Palestinian medical facilities in Jerusalem and the West Bank.     

The Israeli unit in charges of the Erez crossing, COGAT, told AFP news agency that it will "provide help... as needed."  

UN Middle East envoy Tor Wennesland shared his "heartfelt condolences" to the victims on Twitter.  

wd/fb (AFP, Reuters)