Officials said the blast was caused by ammonium nitrate, commonly used as a fertiliser, that had been ‘unsafely stored’ in a warehouse for six years. Ammonium nitrate is also used as a makeshift explosive.

Lebanese President Michel Aoun declared a three-day mourning period and asserted that a state of emergency should be declared in Beirut for two weeks. He also announced that the government would release 100 billion lira (US$66 million) of emergency funds. An investigation is underway to find the exact trigger for the explosion, with those found responsible looking to face the ‘maximum punishment’ according to Lebanon's Supreme Defence Council.

The explosion caused several buildings near the epicentre of the blast to collapse, and its feared that hundreds could be trapped beneath the rubble. Search and rescue forces are currently being deployed from multiple countries to help uncover those that may be trapped.

Lebanese Prime Minister Hassan Diab said in a televised address on Tuesday: “What happened today will not pass without accountability. Those responsible for this catastrophe will pay the price.”

Diab has since appealed for international assistance in response to the explosion: “I am sending an urgent appeal to all countries that are friends and brothers and love Lebanon, to stand by its side and help us treat these deep wounds.” Israel, Qatar, Iraq, Kuwait, Australia, the European Union, the UK and the US are among those who have offered their aid and resources to Beirut.

Beirut being a popular destination among international travellers, officials from different countries have also asserted that its likely their own citizens are among the dead and wounded in Beirut.

“We cannot for the moment exclude German nationals figuring among the dead and wounded,” the German Foreign Ministry said in a statement, while the UK’s Prime Minister Boris Johnson said: “The UK is ready to provide support in any way we can, including to those British nationals affected.”