As investigations continue into an illegal international people smuggling operation, it has been revealed all 39 victims found in the back of a truck near London were Vietnamese.

British police also announced a second man has been charged with multiple counts of manslaughter overnight after the bodies were found in a refrigerated container on an industrial estate on October 23.

The tragic discovery of the bodies has shone a spotlight on the illicit trade that sends the poor of Asia, Africa and the Middle East on perilous journeys to the West.

Vietnam’s Foreign Ministry spokeswoman Le Thi Thu Hang said on Saturday that human traffickers must be strictly dealt with as the Southeast Asian country was informed that several of its citizens were among the victims.

“The Vietnamese embassy in Britain was informed by Essex police that there are Vietnamese citizens, unidentified, among 39 victims in the lorry incident,” Ms Hang said in a statement posted on its website.

“Vietnam strongly condemns human trafficking and considers it a serious crime; traffickers must be strictly dealt with,” Ms Hang said.

The alleged truck driver Maurice Robinson, 25, has already been charged over the deaths and appeared in court on Monday, and on Friday detectives said Eamon Harrison, 23, from Northern Ireland, was also accused of 39 counts of manslaughter as well as human trafficking and immigration offences.

Harrison appeared at Dublin’s High Court at the start of proceedings to extradite him from Ireland to Britain. He was remanded in custody until November 11, a court spokesman said.

The container was picked up at Purfleet dock in Essex, east of London after arriving from Zeebrugge in Belgium, by a truck allegedly driven by  Robinson, from Northern Ireland.

Hoang Thi Ai shows a photo of son Hoang Van Tiep, as police in the UK hunt suspects. Photo: AAP

The victims were found not long afterwards. Police have not confirmed the exact cause of their deaths.

They initially said the victims were thought to be Chinese, but on Friday evening they said they were now all believed to Vietnamese.

“We are in direct contact with a number of families in Vietnam and the UK, and we believe we have identified families for some of the victims,” Essex police Assistant Chief Constable Tim Smith said on Twitter.

Vietnamese police said they had arrested two people and summoned others for questioning on Friday after opening a criminal investigation into suspected human trafficking.

After 10 Vietnamese families reported their relatives missing, fearing they were among the victims, Ha Tinh regional police launched a criminal investigation into suspected human trafficking, a statement posted on their website said.

Two people have been arrested and others brought in for questioning, it said.

The investigation would also look at similar incidents that occurred over the last five years.

On October 26, Vietnamese Prime Minister Nguyen Xuan Phuc ordered an investigation into alleged human trafficking activities after revelations some, if not all the victims were from the southeast Asian country.

One young woman’s final message

A distressing final text message emerged on October 25 from a young woman named as 26-year-old Pham Thi Tra My.

“I’m sorry, Mum and Dad. My path abroad was not a success. I love you both so much.

“I can’t breathe. I’m from Nghen Town, Can Loc District, Ha Tinh, Vietnam … I am sorry, Mum.

The message reportedly came from Ms Tra My’s family, and was received two hours before the trailer arrived at the terminal from Zeebrugge.

Hoa Nghiem from Human Rights Space, a civic network based in Vietnam, said Ms Tra My had gone to China and was planning to reach England via France, the ABC reported.

In the past four weeks, the Hanoi-based organisation has been getting more alerts about possible Vietnamese victims in the trunk.

This is the screenshot of Tra My's last text and her photo, posted with permission from her family's contact. pic.twitter.com/8ErWHBPrbJ

— Hoa Nghiem (@HoaNghiem3) October 25, 2019

Ms Hang said in the statement that Vietnam was working closely with British police to verify victims’ identities and called on other countries to cooperate in combating human trafficking crimes.

“This is a humanitarian tragedy,” Ms Hang said.

“We are deeply saddened and we would like to share our deepest condolences to the families of the victims and wish them to overcome this great pain and loss soon.”

British police also appealed on Friday to Ronan Hughes, 40, and his brother Christopher, 34, from Armagh in Northern Ireland, who they said were crucial to their inquiries. They are wanted on suspicion of manslaughter and human trafficking.

Daniel Stoten, the officer leading the investigation, said police had spoken by telephone to Ronan Hughes recently but needed to question the brothers in person.

“Today I want to make a direct appeal. Ronan and Christopher, hand yourselves in,” Detective Chief Inspector Stoten said.

Lawyers for Global Trailer Rentals, the owner of the trailer, have said Ronan Hughes signed the papers to rent the container, giving an address matching the haulier, C Hughes Transport. Christopher Hughes is listed as a director of C Hughes Logistics Ltd, based in Armagh.

Essex Police are hunting two North Irish brothers for suspected manslaughter. Photo: AP

-with AAP