In an explosion in the port of the Lebanese capital Beirut, dozens died on Tuesday and thousands more were injured. According to local security services, more than 2,700 tons of ammonium nitrate had been stored in the exploded warehouse since 2014. What kind of fabric is this and what is it used for?

Ammonium nitrate is a very water-soluble salt of nitric acid and ammonia. Basically it is mainly used as fertilizer in agriculture. The agent extracts moisture from the soil, so that a lot of nitrogen is released into the soil. This promotes plant growth.

It is also an essential component of ANFO, a mixture of ammonium nitrate and fuel oil, which is widely used as an explosive in mining and has largely displaced dynamite in that sector.

In addition, the substance is regularly used by terrorists when making bombs, because it is relatively easily available due to agricultural use.

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Lebanese in shock and looking for loved ones in city in full rubble

Ammonium nitrate itself is not very flammable

Stored ammonium nitrate, such as in Beirut, does not explode by itself. A confluence of circumstances is needed to lead to such an explosion. This always requires a fuel or external catalytic converter. The substance is not very flammable.

Ammonium nitrate is a so-called oxidizing agent: it enhances combustion and ensures that other substances can ignite more easily.

That is why strict regulations apply to the storage of ammonium nitrate in most countries. For safety reasons, it should be kept away from fuels and heat sources.

See also: More than 2,700 tons of ammonium nitrate was stored unsafely in exploded warehouse Beirut

More frequent explosions with ammonium nitrate

In the past, ammonium nitrate has been at the root of large - mainly industrial - explosions more often.

For example, in 2013, a fertilizer factory in the US state of Texas went up in the air with fifteen deaths and 31 people died in an accident in a chemical factory in Toulouse, France.

Terrorist groups, such as the Taliban, have used the drug to make (improvised) bombs. Ammonium nitrate was also a part of the bomb in the attack in the American city of Oklahoma City in 1995.

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Big fireball and shock wave in explosion in Beirut

'Smaller explosions preceded mega-explosion'

Judging by video footage, the mega-explosion in Beirut probably preceded smaller explosions, according to experts.

"The fire made everything explode," explosives expert Ad van Riel said in the NOS Radio 1 News on Wednesday morning .

"Pressure was building up at the bottom of the fire. At one point it was enough to trigger a mass explosion. Then 2,700 tons of ammonium nitrate is really enormous," says Van Riel.

Check out our live blog for the latest information on the Beirut explosion.