Three days after a massive explosion rocked Beirut, killing at least 149 people and causing widespread devastation, rescuers are still searching for survivors and the government is investigating what caused the disaster.

Here’s what we know at this point:

A CATASTROPHIC TOLL

Tuesday’s blast killed at least 149 people and wounded more than 5,000. It struck with the force of an earthquake, blowing out windows and doors across the capital and leaving several city blocks littered with broken glass, rubble and demolished vehicles. It was the biggest explosion ever seen in the city, which was split in half during the 1975-1990 civil war and has a long history of bombings and terror attacks. Authorities estimate that 300,000 people were initially left homeless — about 12% of the city’s population — and that the city will need $10 billion to $15 billion to rebuild. The blast also obliterated the main port of a tiny country that relies on imports, and shredded a towering silo that had held an estimated 85% of Lebanon’s grain.

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A WAREHOUSE FULL OF EXPLOSIVES

The blast appears to have been caused by the ignition of a stockpile of 2,750 tons of ammonium nitrate, a chemical used in fertilizers and explosives, that had been stored at the port since it was seized from an impounded cargo ship in 2013. Video footage shows a fire at the port, with what appear to be fireworks going off, before a massive explosion rocks the city and sends a mushroom cloud into the sky. It’s unclear what caused the fire, but there is so far no evidence of an attack.

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AN ONGOING INVESTIGATION

The government has launched an investigation that appears to be focused on port and customs officials, with at least 16 employees detained and others brought in for questioning. Officials at the port have sought to shift blame, saying they warned senior officials of the dangers posed by storing a huge amount of ammonium nitrate in a civilian port but that no action was taken. Many Lebanese place the blame squarely on the political class that rose to power during the civil war, which is widely seen as corrupt and incompetent. Scattered protests have broken out, with some people chanting “revolution,” and more unrest seems likely as the full extent of the tragedy sinks in.

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A COUNTRY ALREADY ON THE BRINK

Lebanon was already in the grip of a severe economic crisis rooted in decades of misrule that spawned mass protests last autumn. The currency has plunged in recent months, leading to a painful spike in the prices of basic goods and wiping out many people’s life savings. The explosion sent thousands flooding into hospitals that were already strained by the coronavirus pandemic, potentially worsening the country’s outbreak. Tens of thousands of people have been forced to move in with friends or relatives, which could also accelerate the spread of the virus. One major hospital was forced to close after it was severely damaged.

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AID APPEARS ELUSIVE

Several countries have dispatched emergency aid and search-and-rescue crews to Beirut. But foreign donors are unlikely to provide the sustained, large-scale assistance Lebanon needs without substantial reforms by the country’s long-entrenched political leadership. The government, which defaulted on its sovereign debt in March, has been negotiating an emergency bailout from the International Monetary Fund for months, but the talks faltered over Lebanese infighting and resistance to demands for reform. On Thursday, French President Emmanuel Macron promised aid but also called for a “new political order.” As he toured one of the hardest-hit neighborhoods, an angry crowd vented its fury at Lebanon’s leaders. But while the blast shattered Lebanon’s capital in an instant, its dysfunctional political system remains stubbornly intact.