Truck, which is said to have started its journey in Bulgaria, apparently entered the UK at Holyhead, a North Wales port.
Two members of an international people-smuggling gang were convicted of manslaughter on Monday, over the deaths of 39 people who were found in the back of a container truck in southeast England.
The victims, Vietnamese nationals aged between 15 and 44, were found on October 23, 2019, inside a refrigerated container that had arrived by ferry from Belgium.
There were no survivors in the tragedy.
They came from impoverished villages and are believed to have paid people-smugglers to take them on risky journeys to better lives abroad.
Delivering its verdict, a jury at London’s Central Criminal Court found Eamonn Harrison, a 24-year-old truck driver from Northern Ireland, guilty of 39 counts of manslaughter and one count of conspiracy to assist unlawful immigration.
Kelly Matthews of Britain’s Crown Prosecution Service said: “Nothing can bring back the lives lost on that day or the loss caused by the horrible, unlawful and dangerous actions of these defendants.
“But we hope these convictions bring some measure of solace to the families in the knowledge that justice has been done.”
Gheorghe Nica, 43, from Essex in southeast England, was found guilty of the same charges at the conclusion of the 10-week trial at the London court, commonly known as the Old Bailey. Two others had already pleaded guilty to being involved in the deaths.
Both will be sentenced later. The maximum sentence for people-smuggling is 14 years in prison, while manslaughter carries a maximum life sentence.
The victims – 31 men and boys and eight women – were discovered at an industrial estate in Grays, Essex, about 20 miles (32km) east of central London.
They had been sealed inside the truck’s trailer, which had earlier arrived on a cargo ferry from the Belgian port of Zeebrugge, for at least 12 hours.
Most of those who died were from Nghe An and Ha Tinh provinces in north-central Vietnam, where poor job prospects, environmental disasters and the promise of financial reward abroad fuel migration.
The incident shocked the United Kingdom and Vietnam, shining a spotlight on the illicit global trade that sends the poor of Asia, Africa and the Middle East on perilous journeys to the West.