Several Albanian citizens were arrested, accused of transporting illegal immigrants from Belgium to the United Kingdom.
One of them has admitted the charges, but the other four have denied the criminal offense.
The Albanians used a small boat to travel to Belgium, pick up the migrants and return them to Margate in Kent.
Twelve migrants, believed to be Albanian nationals, including a child, were taken into custody by Belgian authorities, while a boat was later seized in Brightlingsea, Essex, the NCA said.
