Another truck driver from Northern Ireland, Eamonn Harrison, 22, has also been charged in Ireland in the case. He faces counts of manslaughter, human trafficking and immigration offenses but last week challenged attempts to extradite him to Britain.

Separately on Thursday, officials in Ireland began an investigation after 16 migrants were found in a sealed truck container on an overnight ferry traveling from France to Ireland. Some sought asylum. On Sunday, the police said, nine of the men in the group were missing, according to local news reports.

Days before, eight people, including four children, who said they were from Afghanistan were discovered in a refrigerated truck headed to Britain from the port city of Calais, France, local news outlets reported. They were taken to the hospital with signs of hypothermia. Also this month, 31 Pakistanis were found in a truck in southern France near the border with Italy, French prosecutors said.

In the Essex case, after initially identifying the victims as Chinese, the police said this month that they were all from Vietnam and released all 39 names. The victims had set out from Vietnam seeking better lives in Europe and were transported in a trailer from Zeebrugge, Belgium, to the industrial park in Grays.