An initial explosion of pink smoke in the Beirut port late on Tuesday afternoon was followed by a second more devastating explosion that destroyed large parts of the city where important buildings are situated.

Firefighters en route to extinguish the initial explosion were killed by the second explosion.

Lebanon's internal security chief Abbas Ibrahim said that a massive blast in Beirut's port area occurred in a section housing highly-explosive ammonium nitrate, and not explosives as had been reported earlier by the official state news agency NNA.

Al Jazeera reported that most people in Lebanon only learnt about the 2 750 tonnes of ammonium nitrate stored at the city's port after the explosion.

Footage of the blast shared around by residents on social media showed a column of smoke rising from the port district followed by an enormous blast. Those who filmed were thrown backwards by the shock, Reuters reported.

The deafening second blast of the ammonium nitrate - used in bombs and fertilisers - sent an enormous orange fireball into the sky, with a tornado-like shockwave piercing through the city, shattering windows kilometres away and flattening the harbour district.

Wounded people could be seen bleeding amid the dust and rubble in videos posted online after the blast.

Getty Images Marwan Naamani/picture alliance via Getty Images

The videos also showed the extent of the damage caused by flying debris that had punched holes in walls and furniture.

"It is a disaster in every sense of the word," Lebanon's health minister Hamad Hassan said in an interview with several television channels while visiting a hospital in the Lebanese capital.

In the aftermath, the alarms of vehicles damaged in the explosion could be heard across the city, as emergency workers made their way to affected areas.

The New York Times reported that the Kataeb political party's secretary-general, Nizar Najarian, was among those killed in the blast. Kamal Hayek, the chairman of the state-owned electricity company was injured in the blast.

The Guardian reported that the blast destroyed crucial grain silos at the port, which are thought to have stored around 85% of the country's grain.

Lebanon's state-run national news agency quoted Raoul Nehme, the minister of economy and trade, as saying that all the wheat stored at the facility had been contaminated and couldn't be used.

What has happened since?

On social media, residents of Beirut desperate to find loved ones missing in the explosion have been sharing pictures of relatives and their cellphone numbers online.

A page, locatevictimsbeirut, has been set up on Instagram to try to find missing people.

Hundreds of people were still trapped under rubble a day after the explosion, Haaretz reported.

Meanwhile, hospitals across Beirut asked people with non-life-threatening injuries to stay at home because they were unable to cope with a huge influx in patients in the aftermath of the explosion.

In addition, several hospitals were damaged in the explosion, with medical staff in the Gemmayze district being forced to treat patients in a car park.

Getty Images Houssam Shbaro/Anadolu Agency via Getty Images

Hospitals, already under strain from the coronavirus pandemic, also reported shortages of key medicines, including antibiotics.

All available ambulances from North Lebanon, Bekaa and South Lebanon were being dispatched to Beirut to help patients, The New York Times reported.

Local broadcasters earlier reported that the Lebanese Red Cross called for urgent blood donations to help treat injured individuals.

Shortly after the blast, France announced it was sending two planes with dozens of emergency workers, a mobile medical unit and 15 tonnes of aid to Lebanon, a former French protectorate.

French President Emmanuel Macron's office said the aid would allow for the treatment of roughly 500 victims.

Additionally, French peacekeepers stationed in Lebanon have been helping local authorities since the explosions.

Egypt said it opened a field hospital in Beirut, and neighbouring Jordan announced that it would dispatch a military field hospital with all necessary personnel, The Guardian reported.

Beirut's governor estimated that the damage could cost between $3 billion and $5 billion, EuroNews reported.

What was the cause of the explosion?

Ibrahim said the cause of the explosions was not immediately known, but that confiscated explosive materials had been stored at the city's port.

Lebanon's Prime Minister, Hassan Diab, also blamed the catastrophe on the explosion of 2 700 tonnes of ammonium nitrate which had reportedly been stored in the area since 2014. It was confiscated by officials in 2013.

Getty Images Marwan Naamani/picture alliance via Getty Images

Public records and documents published online show senior Lebanese officials knew for more than six years of the dangers it posed, Al Jazeera reported.

Diab vowed that those responsible for the two massive blasts in Beirut's port would be held accountable

US President Donald Trump said the explosion was possibly a part of an attack, SkyNews reported.

Meanwhile, neighbouring Israel, which has strained relations with Lebanon, said the country had nothing to do with the blast.

Israel's defence minister Benny Gantz offered Lebanon humanitarian aid.

"Israel has approached Lebanon through international security and diplomatic channels and has offered the Lebanese government medical and humanitarian assistance," Gantz said in a statement.