Police have searched two addresses in Northern Ireland as officers continue to question a man over the discovery of 39 bodies in a refrigerated lorry trailer in Essex yesterday.
The searches on the properties in County Armagh, carried out last night, are believed to be in connection to the arrest of the driver.
The 25-year-old Northern Irish man remains in custody for questioning by Essex Police on suspicion of murder.
Thirty-eight adults and one teenager, according to “early indications”, were found dead in the lorry and are yet to be identified.
Initial inquiries suggested the trailer containing the victims had arrived in the UK via Holyhead in north Wales but investigators have now said it arrived at Purfleet in Essex from Zeebrugge in Belgium at around 12.30am on Wednesday.
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 nearby Grays.
Eric Van Duyse, a spokesman for the Belgian federal prosecutor's office, said that Brussels had started an investigation into the incident, adding that authorities had “no idea” how long the lorry spent in the country.
The truck was registered in Bulgaria but the country’s ministry of foreign affairs have said it was “under the name of a company owned by an Irish citizen”.
The Prime Minister said the perpetrators of the crime "should be hunted down", while local MP Jackie Doyle-Price said the people smugglers responsible must be caught.
Police have said tracking route used "will be a key line of inquiry".