Police have begun the task of moving the 39 bodies found in a refrigerated trailer attached to a lorry in Essex as a 25-year-old man remains in custody on suspicion of murder.
Detectives were granted more time to question the driver of the truck, named locally as Mo Robinson from Northern Ireland, after eight women and 31 men were discovered dead on Wednesday.
All were believed to be Chinese nationals.
On Thursday evening, the first 11 victims were moved by a private ambulance with a police escort from the Port of Tilbury to Broomfield Hospital in Chelmsford.
The remaining bodies will be transported in stages, with police expecting all the victims to be moved to hospital by the end of the week.
Post-mortem examinations will be carried out, but police warned the investigation will take “some considerable time”.
Essex Police Chief Constable Ben-Julian Harrington said he had the “utmost confidence” in his officers as the force leads its largest-ever murder investigation.
Irish police are conducting follow-up inquiries in relation to the registrations and movements of the refrigerated container and the Irish-owned truck.
Three addresses have been searched in Northern Ireland as part of the probe.
Councillor Paul Berry said the village of Laurelvale, where the Robinson family live, was in “complete shock”.
Irish company Global Trailer Rentals Ltd (GTR) confirmed it owned the refrigerated part of the lorry and a spokesman said the company was “shellshocked” and “gutted” by the news.
The firm said the trailer had been leased on October 15 from its rentals yard in Co Monaghan, in the Republic of Ireland, at a rate of 275 euro (£237) a week.
It said it provided police with information about the person and company that leased the trailer, as well as offering to make tracking data available.
The trailer arrived at Purfleet from Zeebrugge in Belgium at around 12.30am on Wednesday, and the front section to which it was attached, known as the tractor, came from Northern Ireland via Holyhead in North Wales on Sunday.
The lorry and trailer left the port at Purfleet shortly after 1.05am and officers were called to the Waterglade Industrial Park on Eastern Avenue in Grays at 1.40am.
Questions have been raised about when the victims entered the sealed refrigerated trailer, where temperatures can be as low as -25C, as well as the full route of the unit.
Joachim Coens, chief executive of Zeebrugge port, from where the lorry trailer departed, said it was unlikely people were loaded into the container at the Belgian site.
Mayor Dirk De Fauw, also the chairman of the port of Zeebrugge, said it was “virtually impossible” the victims went into the trailer at the Belgian border.
He told Belgian media: “Each trailer is systematically checked to look for outward signs of damage. Then it is sealed. Trailers are filmed until they are on the ferry.
“In the terminals too there are cameras. Breaking the seal, putting 39 people in a trailer and resealing the trailer without anybody noticing is virtually impossible.”
A spokesman for C.RO Ports, which operates terminals at Purfleet and Zeebrugge, said the firm would “fully assist” the police investigation, while the Chinese ambassador to the UK, Lui Xioaming, said the Chinese embassy had sent a team to Grays to meet with police.
Vigils have been held in London and Belfast to pay tribute to the victims and a book of condolences has been opened in Grays.