The deadly stampede in Seoul's Itaewon district on Saturday has once again revealed the danger of crowd surges.

It still remains unknown how the stampede in Seoul began. Experts say it is extremely difficult to escape when involved in such accidents. They warn people to stay away from crowds, especially in narrow spaces.

Experts say when people get so packed together that they cannot move, there is a point when they fall over one another.

They explain bodies on top of people on the ground exert so much pressure, even breathing becomes extremely difficult.

There have been many accidents involving crowd surges.

In Japan, a stampede on a crowded footbridge killed and injured many people in the western city of Akashi, Hyogo Prefecture, in 2001.

Other countries have also seen similar accidents in the past, such as during the Hajj pilgrimage in Saudi Arabia.