What is ammonium nitrate and how did it get to the port?

Ammonium nitrate an industrial chemical commonly used for fertilisers, but also as an explosive, often used in mining.

The chemical, known by the formula NH4NO3, is a naturally white crystalline solid and is often known as saltpetre.

Under most conditions ammonium nitrate is not necessarily dangerous and is relatively stable - it can even be used to smother a fire.

However, if contaminated it can become highly volatile.

Read more by Alex Macdonald on previous incidents involving Ammonium Nitrate and how it ended up in Beirut Port