On Tuesday evening, Lebanon's capital Beirut was rocked by an enormous twin explosion, heard as far away as Cyprus, which devastated the city.
It is the largest destruction the previously war-torn city has seen in decades and pictures emerged of collapsed buildings and shattered windows tens of kilometres away from the blast site.
Lebanon was already on the brink of collapse, with a severe economic crisis that has ignited mass protests in recent months. Its hospitals – many of which suffered damage – were struggling financially even before the coronavirus pandemic began earlier this year. When the thousands of wounded started to arrive, they were quickly overwhelmed.
What caused the explosion?
Prime Minister Hassan Diab said an estimated 2,750 tonnes of the agricultural fertiliser ammonium nitrate that had been stored for years in a "dangerous" portside warehouse had blown up.
Local TV station LBCI said that workers welding a door at the warehouse on Tuesday started a fire that ignited the chemicals, according to people who attended a Higher Defence Council briefing after the blast.
Ammonium nitrate is an odourless crystalline substance commonly used as a fertiliser that has been the cause of numerous industrial explosions over the decades. When combined with fuel oils, it creates a potent explosive widely used by the construction industry, but also by insurgent groups like the Taliban for improvised explosives.
Where did the ammonium nitrate come from?
General Security head Maj Gen Abbas Ibrahim said the material had been confiscated years earlier and stored in the warehouse, just minutes from Beirut's shopping and nightlife districts.
The ammonium nitrate arrived as cargo on the ship MV Rhosus in 2014, according to two letters issued by the director general of Lebanese Customs. For reasons that are unclear, dockworkers unloaded the chemical, which can be used to make fertilisers and explosives, and put it into storage.
Read more: A breakdown of the Beirut blast
Customs officials later asked judicial authorities at least twice to issue orders for the ammonium nitrate to be confiscated or re-exported, according to the letters. In one of the letters, dated May 3, 2016, the director general at that time, Shafik Merhe, warned of “the extreme danger” from storing the chemical in a warehouse “in this unsuitable weather”. The material posed a risk to the staff and the port, he said.
Lebanese broadcaster LBCI reported that the Rhosus had been scheduled to sail with its cargo from Beirut six years ago but stayed at the port due to a mechanical failure.
Was the blast ignited by fireworks?
Investigations are ongoing into the cause of the incident. Local TV stations reported initially that a stockpile of fireworks in a nearby warehouse may have cause a fire. Videos showed that the fire appeared to spread, possibly setting off the explosions, the second of which caused a mushroom cloud and generating a shock wave. The involvement of fireworks has not been confirmed, and it is now thought that it could have been as a result of the welding.
Under normal storage conditions and without a very high heat, it is difficult to ignite ammonium nitrate, supporting the theory that a smaller incident led to the secondary explosion.
How many people are dead and injured?
An official with the Lebanese Red Cross said at least 158 people were killed and more than 6,000 were wounded, with some still missing. The death toll is expected to rise as overburdened hospitals continue to treat victims of the blasts, with at least 100 people still missing.
Among the dead are a few foreign nationals. Architect Jean-Marc Bonfils from France died, while a further 24 French people were injured. A German diplomat also died, as did the wife of the Dutch ambassador.
What’s the damage?
Even 10 kilometres from the blast at Beirut airport, ceilings fell down and windows broke.
Read More: Beirut before and after the explosion
What is the government doing?
Information Minister Manal Abdel Samad and Environment Minister Damianos Kattar both announced their resignations on Sunday, in a further hit to the embattled government of Prime Minister Hassan Diab.
Calling the explosion an "enormous catastrophe", Mr Kattar said he had lost hope in a "sterile regime that botched several opportunities".
The government has given an "investigative committee" four days to determine responsibility, and Foreign Minister Charbel Wehbe told French radio they will be punished for "this horrible crime of negligence".
The government has also declared a two-week state of emergency and handed security of the capital to the army.
An investigation has been ordered by President Michel Aoun. Separately, MPs have set up a committee to carry out another investigation that they say requires international assistance because of the number of high-ranking senior officials implicated in negligence that led to the explosion.
While the investigations go on, cabinet has ordered the army to place an undisclosed number of port officials under house arrest.
How have Beirutis reacted?
Hundreds took to the streets on Saturday and Sunday night to protest the government's apparent complicity in the disaster. They stormed some of the ministries to denounce the corruption of their leaders, some carried mocked-up gallows and nooses.
Many of the people in Beirut are simply shocked by the extent of the devastation. Some are leaving their shattered homes to move out of the city until it’s safe to go back, while others are opening their doors, despite the Covid-19 pandemic, to offer shelter to those who lost everything.
People are also setting up food and water distribution points, handing out clothes and supplies.
Hundreds have lost pets in the chaos and confusion. But local shelter Animal’s Lebanon is trying to help re-unit lost animals with their owners and offer care to injured pets.
What has the international reaction been?
World leaders and international organisations pledged nearly $300 million in emergency humanitarian aid, but warned on Sunday that no money for rebuilding the capital will be made available until Lebanese authorities commit themselves to the political and economic reforms demanded by the people.
Over 30 participants to an international conference offered help for a “credible and independent” investigation, another key demand of the protesters. World leaders offered help in the form of aid and field hospitals.
French President Emmanuel Macron landed in Beirut on Thursday. He said Lebanon was facing a political and economic crisis, and that it would continue to suffer unless it enacted reforms.
"We must act quickly and efficiently so that this aid goes directly to where it is needed," Mr Macron said.
"We must all work together to ensure that neither violence nor chaos prevails. It is the future of Lebanon that is at stake."
The World Health Organisation said it will airlift medical supplies to Lebanon to cover up to 1,000 trauma interventions and up to 1,000 surgical interventions.
WHO spokesman Tarik Jasarevic said supplies airlifted from a "humanitarian hub" in Dubai in the United Arab Emirates would be used to treat burns and wounds caused by broken glass and other debris from the explosion.
Rescue teams flew in on Wednesday and Thursday from France, Russia, the Czech Republic and elsewhere. Jordan, Egypt, Russia and France were flying in field hospitals and medical staff to assist.
United Nations chief Antonio Guterres expressed his "deepest condolences," saying the attack had also injured some UN personnel.
Saudi-funded medical teams were dispatched from north Lebanon to Beirut to care for and to help transport the wounded on Tuesday, while a specialised team from a medical centre provided emergency health care services in the Lebanese capital, according to the state-run Saudi Press Agency.
Prosecutors in France also opened an investigation into "involuntry injury" on Wednesday – 21 French nationals were wounded in the devastating blast.