The 39 people found dead in the back of a lorry in Essex were Chinese nationals, sources said.
Thirty eight adults and one teenager was discovered inside the container at an industrial estate in Grays in the early hours of yesterday morning.
Following the discovery the 25-year-old driver - named as Mo Robinson of Portadown, Northern Ireland - was cuffed on suspicion of murder .
As a result two addresses in Co Armagh were raided.
Councillor Paul Berry said the village of Laurelvale, where the Robinson family live, was in "complete shock".
Detectives have said the trailer containing the victims arrived at Purfleet from Zeebrugge in Belgium at around 12.30am on Wednesday and the front section to which it was attached, known as the tractor, came from Northern Ireland.
The lorry and trailer left the port at Purfleet shortly after 1.05am and officers were called around 30 minutes later after ambulance staff made the grim discovery at Waterglade Industrial Park in Eastern Avenue in nearby Grays.
Eric Van Duyse, a spokesman for the Belgian federal prosecutor's office, said that Brussels had started an investigation into the incident.
He added: "We have no idea at the moment how long the lorry spent in Belgium, it could be hours or days, we just don't know."
Police have said tracking route used "will be a key line of inquiry".
The Bulgarian ministry of foreign affairs said the truck was registered in Varna in Bulgaria "under the name of a company owned by an Irish citizen".
It is not known if the young dad-to-be was working for a haulage firm or whether he owned his own truck.
Officers from Essex Police have started to remove the bodies from the trailer and attempted to identify them.
