Four men have been arrested in a people smuggling investigation after 10 people, mostly under-18s, were found in the back of a lorry in Belgium.
The lorry was searched by the Belgian authorities near Ghent on Thursday after they received information from the UK's National Crime Agency (NCA).
The lorry driver, a 64-year-old man from Glasgow in Scotland, was arrested.
Two Irishmen were later arrested in Dover, England, and a fourth man was detained in Northern Ireland.
The UK arrests were made by the NCA and searches have also been carried out at properties in Kent and in Cushendall, County Antrim.
Two suspected firearms were seized at an address in Kent.
The Irish nationals arrested in Dover are aged 39 and 48.
The man arrested in Northern Ireland is 30 years old and was detained after presenting himself to Antrim police station following contact between the NCA and his lawyers.
All three are being questioned by NCA investigators on suspicion of facilitating illegal immigration.
The lorry was carrying tyres when it was stopped and searched.
The people discovered in the back of the vehicle are thought to be from south east Asia.
Two of them are adults and eight are juveniles, according to the NCA.
Its regional head of investigation, Gerry McLean, said they had been put at great risk.
"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," he said.
"We have seen only recently in Essex the tragic consequences which these types of attempts can have."
Mr McLean was referring to the deaths of 39 Vietnamese migrants whose bodies were found in a lorry in Essex in October.
Belgian 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."