On August 4, 2020, approximately 2,750 tonnes of ammonium nitrate exploded at the port of Beirut, Lebanon, producing a blast equivalent to roughly 1 kiloton of TNT. The explosion killed over 200 people, injured thousands more, and left an estimated 300,000 people homeless. It ranks among the largest non-nuclear explosions in history.
How Ammonium Nitrate Ended Up at the Port
The ammonium nitrate arrived in Beirut in November 2013 aboard the MV Rhosus, a Russian-owned, Moldovan-flagged cargo ship. The vessel had departed from Batumi, Georgia, and was heading to Beira, Mozambique. It made an unscheduled stop in Beirut, where port authorities detained it over safety violations and unpaid fees. The crew eventually abandoned the ship.
Rather than disposing of the cargo or shipping it onward, authorities offloaded the 2,750 tonnes of ammonium nitrate into Hangar 12 at the port, where it sat for nearly seven years. Ammonium nitrate is widely used as agricultural fertilizer, but it becomes classified as an explosive when mixed with more than 0.2% combustible material. Storing that quantity in an urban warehouse, alongside fireworks, was extraordinarily dangerous.
Six Years of Ignored Warnings
Port, customs, and security officials knew the danger. Starting shortly after the ammonium nitrate was stored, officials wrote to judges roughly every six months asking for the material to be removed from its position so close to the city center. Reuters reported that a letter was also sent directly to Lebanon’s president and prime minister in July 2020, just weeks before the explosion. None of these warnings led to action.
What Triggered the Blast
The catastrophe began about 30 minutes before the main explosion, when a fire broke out inside Hangar 12. The exact ignition source has been disputed, with reports pointing to welding work being done on the hangar door. The fire spread to fireworks stored in the same warehouse, producing the smaller explosions and crackling sounds captured in widely shared videos. That fire then reached the ammonium nitrate stockpile, detonating the massive blast.
The Scale of the Explosion
Researchers from multiple disciplines worked to calculate the blast’s power. A study published in Scientific Reports combined seismic, acoustic, and satellite data to estimate the yield at between 0.13 and 2 kilotons of TNT, with a central estimate near 1.1 kilotons from seismic analysis alone. For context, that is roughly one-fifteenth the size of the atomic bomb dropped on Hiroshima, but concentrated in the heart of a dense urban port.
The explosion registered on seismographs as far away as Europe. It created a visible shockwave that rippled across the city, shattering windows kilometers from the blast site and destroying roughly 70,000 homes. A World Bank rapid assessment estimated physical damage between $3.8 and $4.6 billion, with additional economic losses of $2.9 to $3.5 billion. Housing and cultural heritage sites suffered the most severe damage.
Toxic Fallout and Air Quality
The distinctive reddish-brown cloud that rose over Beirut was nitrogen dioxide, a toxic gas released when ammonium nitrate detonates. The explosion also produced ammonia and nitric oxide. Satellite measurements showed nitrogen dioxide concentrations at unhealthy levels across large areas of Beirut and even into western Syria. Atmospheric conditions pushed the toxic plume downward toward ground level, increasing exposure for residents and the roughly 5,000 people displaced into the streets.
Short-term exposure to these gases causes eye and skin irritation, respiratory problems, coughing, headaches, and nausea. Nitrogen dioxide levels took about seven days to return to normal.
The Grain Silos and Food Security
Just 75 meters from the explosion’s epicenter stood Beirut’s grain silos: 42 concrete cylinders capable of storing up to 120,000 tonnes of grain, enough to make bread for 1.7 million people. The silos had been a cornerstone of Lebanon’s food security since the 1970s, receiving regular shipments of wheat, barley, and corn from the Black Sea region.
The blast gutted the silos but left portions of the structure standing. An estimated 10,000 tonnes of spilled grain remained at their base, and fires began igniting in the decaying grain as early as December 2020. In July 2022, a fire broke out at the base, and the cycle of heating and rapid cooling destabilized what remained. The northern section of the silos collapsed in three stages over the course of a month, on July 31, August 4, and August 23 of 2022. Their destruction compounded an already severe food crisis in a country experiencing economic collapse.
The Stalled Investigation
More than four years after the explosion, no one has been held accountable. Judge Tarek Bitar was appointed to lead the investigation, but the probe has faced persistent obstruction. Officials implicated in the case accused Bitar of bias, refused to testify, demanded his removal, and filed legal complaints against him. In 2023, the chief prosecutor at the time ordered the release of 17 detainees, including port and customs officials who had been held since the explosion. Bitar and legal experts condemned that move as unlawful.
Bitar has since resumed the probe and planned to question senior officials, but the investigation’s repeated suspensions have left victims’ families with no formal accounting of how a known danger was allowed to sit in a warehouse for nearly seven years in the middle of a capital city.