The Belgian authorities were acting on information from the NCA, and arrested the driver of the vehicle, a 64-year-old man from Glasgow, following the discovery of 10 migrants in a lorry carrying a load of tyres near Ghent in Belgium on Thursday 5 March.
The migrants, believed to be two adults and eight juveniles, are thought to be from south-east Asia.
NCA officers then arrested three further men, two in Dover, Irish nationals aged 39 and 48, on suspicion of facilitating illegal immigration. A 30-year-old man was subsequently arrested in County Antrim, Northern Ireland, today (Friday 6 March).
All three are now in custody being questioned by NCA investigators, while officers have also carried out searches at properties in Northern Ireland and Kent. At an address in Kent two suspected firearms were seized.
NCA regional head of investigation Gerry McLean said: “Our close working with our Belgian partners in this instance has led to the safeguarding of a number of migrants who had been put in a very dangerous situation, and we are grateful for their support. We have seen only recently in Essex the tragic consequences which these types of attempts can have.
“Working with partners at home and abroad, we are determined to do all we can to disrupt and dismantle criminal networks involved in illegal immigration, and our investigation into this matter continues.”
West Flanders Prosecutor Frank Demeester added: “This kind of human smuggling is very dangerous, and the operation proves once more that international cooperation works in the fight against this type of organised crime.
“The contacts between the British NCA and Belgian Federal Judicial Police, maritime police and prosecutors have become more intense in recent years.
“In the fight against human smuggling, the UK is obviously an important partner as being the country of destination.”