Britain and other European countries must accept some responsibility for the deaths of 39 people, believed to be Chinese nationals, found dead in a refrigerated truck near London, China's state-backed Global Times says.

Paramedics and police found the bodies of 31 men and eight women on Wednesday on an industrial estate at Grays in Essex, about 30km east of the British capital.

For years, illegal immigrants have stowed away in trucks while attempting to reach Britain, often from the European mainland. In 2000, 58 Chinese were found dead in a tomato truck at the port of Dover.

At the moment it was impossible to say how much responsibility the dead should bear for the tragedy, the widely-read Chinese newspaper said in an editorial.

"But such a serious humanitarian disaster has occurred under the eyes of the British and Europeans," it said. "It is clear that Britain and relevant European countries have not fulfilled their responsibility to protect these people from such a death."

Even if found to have been smuggled into the country, the victims' death was not their fault, added the paper, which is published by the ruling Communist Party's official People's Daily.

"We hope that Britain and European countries will put into effect their various commitments to human rights and make due efforts for Chinese people to be free from abuse and sudden death."

Britain appears not to have learned its lesson from the Dover incident two decades ago, it added.

A Global Trailer Rentals spokesman has confirmed the company owned the part of the truck found on an industrial estate east of London containing the bodies of the eight women and 31 men. The hire company said it was "shellshocked" and "gutted" after 39 Chinese people were found dead in one of its trailers.

The company said it provided police with information about the person and company that leased the trailer, and offered to make tracking data available.

Its directors said the company was "entirely unaware" the trailer was to be used in the manner it was.

Police have arrested a 25-year-old man from Northern Ireland, named locally as Mo Robinson, on suspicion of murder.

Earlier, police searched two addresses in Northern Ireland.

The searches in County Armagh on Wednesday night are believed to be linked to the arrest of the driver, who remains in custody for questioning by Essex Police.

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Detectives said the trailer containing the victims arrived at Purfleet from Zeebrugge in Belgium about 12.30am on Wednesday and the front section to which it was attached, known as the tractor, came from Northern Ireland.

The truck and trailer left the port at Purfleet shortly after 1.05am and officers were called about 30 minutes later after ambulance staff made the grim discovery at Waterglade Industrial Park in nearby Grays.

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Eric Van Duyse, a spokesman for the Belgian federal prosecutor's office, said Brussels had started an investigation into the incident.

"We have no idea at the moment how long the lorry spent in Belgium, it could be hours or days, we just don't know," he said.

I’m appalled by this tragic incident in Essex. I am receiving regular updates and the Home Office will work closely with Essex Police as we establish exactly what has happened. My thoughts are with all those who lost their lives & their loved ones. — Boris Johnson (@BorisJohnson) October 23, 2019

In 2000, 58 Chinese nationals were found dead, having suffocated, in a truck at Dover.

The latest deaths follow warnings from the National Crime Agency (NCA) and Border Force of the increased risk of people-smuggling via Belgium and into quieter ports such as Purfleet.

The NCA previously said it had a "greater focus" on rising smuggler numbers in Belgium after the closure of a migrant camp, and a Border Force assessment highlighted Zeebrugge as being among "key ports of embarkation for clandestine arrivals".

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The NCA has also warned that criminal networks are suspected to have started targeting quieter ports on the east and south coasts of the UK as well as the main Channel crossing between Calais and Dover.

Speaking on Wednesday afternoon, Deputy Chief Constable Pippa Mills said the truck and the container were being moved to nearby Tilbury Docks so the bodies can be recovered while preserving the dignity of the victims.

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"We are yet to identify them and must manage this sensitively with their families," she said.

Police have said tracking route used "will be a key line of inquiry".

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The Bulgarian ministry of foreign affairs said the truck was registered in Varna in Bulgaria "under the name of a company owned by an Irish citizen".

Police originally thought the truck had travelled to the UK through Holyhead in north Wales on 19 October but later revealed that the trailer had come directly from Europe.

A freight ferry service runs from Zeebrugge to Purfleet.

Shocked & saddened by this utterly tragic incident in Grays. Essex Police has arrested an individual and we must give them the space to conduct their investigations. — Priti Patel MP (@patel4witham) October 23, 2019

Security checks for people smuggling are believed to be less stringent at both ports than at Calais and Dover.

A community in shock after arrest

The father of the truck driver being questioned over the discovery of the 39 bodies learned of his son's arrest through social media, a community representative says.

Councillor Paul Berry said the village of Laurelvale, where the Robinson family live, was in "complete shock".

Mr Berry said Robinson's father "had said he had been getting messages via people on social media on what was happening and at that stage, it was not confirmed to him or his family that his son had been arrested".

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Mr Berry, who knows the father well, said the family were "very well respected" in the area.

"The local community is hoping that (Mo Robinson) has been caught up innocently in this matter but that's in the hands of Essex Police, and we will leave it in their professional hands to try to catch the perpetrators of this."

He said the family had been left upset by the "unwelcome spotlight" the incident had shone on them.

"It was very distressing for the family as they just felt they were captive in their own home," he said.

With additional reporting from AAP and AFP