All of the 39 people found dead in a lorry are believed to be Chinese nationals, Essex Police said on October 24.
Eight of the dead were women and 31 were men, the statement said.
Essex Police said that a 25-year-old lorry driver from Northern Ireland remains in custody.
“We can confirm that three properties in County Armagh have been searched in connection with our investigation,” the statement said.
Bulgarian authorities confirmed on October 23, the day the group of dead people were found in the lorry, that the vehicle was registered in the Black Sea city of Varna, to a company owned by an Irish national. However, the lorry had not been in Bulgaria since 2017.
Essex Police said that the the tractor unit of the lorry had entered the UK via Holyhead on October 20, having travelled over from Dublin.
The lorry then collected the trailer, which had travelled from Zeebrugge, at the port of Purfleet at around 12:30am on October 23. The cab and trailer left the port shortly after 1.05am.
“We were called to Waterglade Industrial Park in Eastern Avenue shortly before 1.40am on Wednesday October 23 by our colleagues in the East of England Ambulance Service to reports that 39 people had been found dead in the trailer of a lorry.”
Of these, 38 are believed to be adults, and one is a young adult woman.
“The lorry has since been removed from the industrial park to allow the next stage of our investigative process to be conducted in peace, and to give the utmost dignity to those within the trailer as we prepare for a coroner’s post-mortem examination.
“Each of the 39 people must undergo a full coroner’s process to establish a cause of death, before we move on to attempting to identify each individual within the trailer. This will be a substantial operation and, at this stage, we cannot estimate how long these procedures will take,” Essex Police said.