Why are children being taken from their parents at the US border?

Children separated from families held in detention centres at the US-Mexico border. Credit: PA

Images of children being held in steel-fence cages at detention centres on the US-Mexico border have shocked the world.

Currently around 2,000 children a month are being forcibly removed from families caught illegally crossing the border.

So, why are these children being separated from their parents?

ITV Multimedia News Producer Nitya Rajan explains.