Beirut explosion rocks Lebanon's capital city

We're still not exactly sure what caused the deadly explosion in Beirut yesterday, but Lebanon's prime minister said an investigation would focus on an estimated 2,750 metric tons of the explosive ammonium nitrate stored at a warehouse.

So what is ammonium nitrate? Also known as AN, it's a compound of ammonia and nitrogen, is a highly volatile material used in agricultural fertilizers and bombs.

Disasters involving AN are rare, considering the US uses millions of tons of it every year in fertilizers, according to the Environmental Protection Agency. "Pure" solid AN is quite stable, but if the compound is mixed with any contaminants, even in small traces, the mixture becomes much more prone to detonation  — which is why there are normally stringent government guidelines for how to treat and store it properly.

For instance, AN shouldn't be stored with any fuel, organic materials, chlorides or metals, said the guide — all potential contaminants. The EPA guidelines also recommend fire resistant walls in the storage unit, noncombustible flooring, and — crucially — controlled temperatures.

AN doesn't burn, but if exposed to heat, it can melt — which releases combustible toxic gases that can cause an explosion. It's even more dangerous if there is a large supply of AN all stored together, because once a small section of AN begins to melt and explode, the resulting heat can set off the rest of the supply.

Some history: One of the worst disasters in US history involving a form of ammonia occurred in April 1947 when a ship loaded with ammonium nitrate caught fire while docked in Texas City. The fire caused an explosion and additional fires that damaged more than 1,000 buildings and killed nearly 400 people, according to the website of the Texas Historical Association.

For perspective, that explosion was triggered by 2,300 US tons (about 2087 metric tons) of ammonium nitrate, according to US Homeland Security.

And the 1995 Oklahoma City Bombing, a US domestic terror attack that killed 169 people and injured 467, used only two US tons (1.8 metric tons) of ammonium nitrate.

This satellite image from Planet Labs, Inc, showed the destruction left in the wake of yesterday's deadly explosion in Beirut.

At least 100 people were killed in the blast, and the death toll could rise as many more people are reported missing. At least 4,000 people were injured in the explosion.

For comparison, here's what the port area looked like before the blast:

The Lebanese cabinet has ordered that “officials” involved in the Beirut port explosion be placed under house arrest “in the coming days,” the Lebanese Minister of Displaced People Ghada Shreim said without providing further details.

Every single business in Beirut has been affected by yesterday's deadly blast, Lebanon's Economy Minister Raoul Nehme said.

“There is not one apartment in Beirut that wasn’t impacted, not one businesses that wasn’t impacted – whether the storefront of the goods” he said. 

”The impact on the economy is massive and the port has been practically erased,” Nehme told CNBC Arabia in an interview Wednesday, adding it was too soon to fully gauge the scale of the damage on the economy. 

He said the government’s priority was to secure people’s basic necessities – mainly food but also supplies to help repair the extensive damage to homes and infrastructure across the city. 

Turkey is sending search and rescue teams, health care workers, medical supplies and other urgent humanitarian aid to help in the aftermath of the blast in Beirut, according to the Turkish foreign ministry.

Turkey is also planning on setting up a field hospital, the ministry said in a written statement. 

Qatar sent a plane filled with medical supplies to Lebanon to help victims of the Beirut explosion, according to a tweet from the Qatari government.

The first plane arrived today, and the government will send three more carrying equipment for hospitals.

Lebanon's Health Minister Hamad Hassan said Tuesday’s explosion that killed at least 100 people and wounded 4,000 added to the country's health care system crisis as it has been already struggling with the Covid-19 pandemic.

"It requires everyone to engage positively from politicians, political parties, authorities, and from all friendly and brotherly countries because we suffer from a shortage in the number of beds and a lack of equipment to help injured people and those are in critical conditions," Hassan added.

A deadly explosion shook Beirut yesterday. The Lebanon capital's 4 million residents woke this morning to the full horror and scale of the damage to their city, lives, and livelihoods.

If you're just reading in now, here's what we know so far about the massive blast:

Watch CNN's Ben Wedeman report:

At least 300,000 people have been displaced from their homes by Tuesday's devastating explosion, Beirut's governor Marwan Abboud said in an interview with Jordan's state-owned channel Al Mamlaka.

Images and videos from the immediate aftermath of the blast show homes destroyed and covered with shattered glass.

At least 100 people were killed, and 4,000 more were wounded in the explosion, according to state media. That death toll is expected to rise as hundreds remain missing.