Post-mortems are due to be carried out on some of the 39 people who were found dead in a lorry container at industrial estate in Essex.
Eleven of the victims, who are all believed to be Chinese, have been taken by private ambulance under police escort from the Port of Tilbury to Broomsfield Hospital in Chelmsford.
The remaining bodies will be transported in stages and are expected to be moved by the end of the week.
The post-mortems come after the 31 men and eight women were found at Waterglade Industrial Park in Grays in the early hours of Wednesday.
Later that day, they were moved to a more sensitive site at nearby Tilbury Docks as police try to identify them.
Vigils have been held outside the Home Office in London, as well as in Brighton and Belfast, to pay tribute to the victims, and officers and local councillors in Essex have signed a book of condolence.
Flowers have also been left at the entrance to the industrial estate where the discovery was made, which has led to the largest murder investigation ever carried out by Essex Police.
The driver was arrested at the scene after police were called at 1.40am and officers were granted an extra 24 hours of custody time to continue questioning him on Thursday.
Sky sources have named the suspect as Mo Robinson, from Portadown.
The lorry cab he was driving had started its journey in Northern Ireland before meeting the trailer in Purfleet.
Irish firm Global Irish Rental said it owned the container and rented it out on 15 October, according to reports.
Police in Northern Ireland have been searching three addresses in County Armagh following the arrest of the driver on suspicion of murder, which is said to have left his family "stunned".
They only found out about the arrest when a picture of Mr Robinson, 25, appeared in the media.
Their local councillor, Paul Berry, told Sky News: "His family are very well respected in the area and are very actively involved in community organisations.
"Our heart goes out to them because as of yesterday morning they were not aware that he had been arrested."
He added: "The community's thoughts and prayers are with the family of the 39 people who have lost their lives. People are devastated but also stunned and shocked that someone local has been arrested."
Belgian authorities believe the container was transported to the UK from Zeebrugge at 2.49pm local time on Tuesday, arriving in Purfleet at around midnight.
CCTV has shown it being driven towards the industrial park at 1.10am, half an hour before Essex Police were called to the scene by ambulance crews.
The Belgian public prosecutor's office said it is "not yet clear" when and where the victims were placed in the container, adding that no further information would be released at this time.
Its statement said it would continue to work with police in the UK to find out what happened - and the Chinese foreign affairs ministry has told Sky News it is also investigating the case.
The Chinese embassy has sent a team to Essex.
The case has echoed a similar incident in 2000, when 58 Chinese people were found dead in a container at Dover.
How the container ended up in Grays
Police believe the trailer travelled on a ship from the port of Zeebrugge in Belgium on Tuesday - where it was before then remains unclear.
Lorry driver Graham Westmorland told Sky News that scanners at Zeebrugge were not up to the job and people were able to get through without being picked up.
From Zeebrugge it headed to Purfleet in Essex, arriving in the early hours of Wednesday.
Essex Police say the lorry cab began its journey to Grays in Northern Ireland, from where it headed to Dublin and then caught a ferry to Holyhead in north Wales.
It made its way to Essex and picked the container up from Purfleet at around 12.30am on Wednesday.
It left Purfleet at 1.05am and was driven to Grays, with CCTV footage showing the lorry driving towards the industrial park minutes before the bodies were found.
The images were taken at 1.10am and show the vehicle just around the corner from where the discovery was made a short time later at the estate.
Police are likely to be looking into the movements of the trailer, which is said to be fitted with a GPS tracking system.
The Bulgarian ministry of foreign affairs said the Scania truck was registered in Varna and prime minister Boyko Borissov said the vehicle had not entered the country since 2017.
Road haulage experts said temperatures in refrigerated units can be as low as -25C.
Officers say people who are concerned about a loved one should call 0800 056 0944, or 0044 207 158 0010 if calling from abroad.