The 39 people found dead in the back of a lorry in Essex were Chinese nationals, sources said.
It is understood that there were men and women discovered in the refrigerated lorry trailer in Grays, Essex, on Wednesday.
The news comes as it was revealed olice 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.
The searches in Co Armagh last night are believed to be linked to the arrest of the driver, named in reports as 25-year-old Mo Robinson, from Portadown.
He remains in custody for questioning by Essex Police on suspicion of murder.
There was no answer at the Co Armagh home of Mr Robinson's family.
Trailer came from the Continent
Detectives have said the trailer containing the victims arrived at Purfleet from Zeebrugge in Belgium 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. Officers were called around 30 minutes later after ambulance staff made the grim discovery at Waterglade Industrial Park in Eastern Avenue in nearby Grays.
Brussels launches investigation
Eric Van Duyse, a spokesman for the Belgian federal prosecutor's office, said that Brussels had started an investigation into the incident.
He said: "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."
The incident follows warnings from the National Crime Agency (NCA) and the Border Force of the increased risk of people-smuggling via Belgium.
Rising smuggler numbers
An NCA assessment report on serious and organised crime last year said there was a "greater focus" on rising smuggler numbers in Belgium after the closure of the Dunkirk migrant camp in 2017.
A Border Force assessment in 2016 highlighted Zeebrugge as being among "key ports of embarkation for clandestine arrivals".
Speaking yesterday afternoon, Deputy Chief Constable Pippa Mills said the lorry and the container were being moved to nearby Tilbury Docks so the bodies can be recovered while preserving the dignity of the victims.
"We are yet to identify them and must manage this sensitively with their families," she said.
Perpetrators 'should be hunted down'
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 the 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".
Police originally thought the lorry had travelled to the UK through Holyhead in north Wales on 19 October, but later revealed the trailer had come directly from the Continent.
A freight ferry service runs from Zeebrugge to Purfleet.
Security checks for people smuggling are believed to be less stringent at both ports than at Calais and Dover.
The discovery comes as the NCA said the number of migrants being smuggled into the UK in containers and lorries has risen in the last year.