Maurice "Mo" Robinson, a 25-year-old resident of Northern Ireland, has been in custody since the bodies of 31 men and eight women were discovered Wednesday in Grays, a town in the English county of Essex, the Efe news reported.
Robinson "is due to appear at Chelmsford Magistrates' Court on Monday 28 October charged with 39 counts of manslaughter, conspiracy to traffic people, conspiracy to assist unlawful immigration and money laundering," Essex Police said in a statement.
"Three other people have been arrested in connection with this investigation," the department said, identifying those suspects as a man and a woman, both 38, from Warrington, England, and a 48-year-old man from Northern Ireland.
Meanwhile, police in the Republic of Ireland on Saturday said they had arrested a man in connection with the investigation at Dublin Port. Police described him as a man in his 20s from Northern Ireland.
Authorities in Vietnam have raised concerns that at least two Vietnamese nationals were among the victims.
Essex Police originally hypothesized that all 39 victims were Chinese.
Two families in Vietnam have come forward, saying they feared that Pham Thi Tra My and Nguyen Dinh Luong, both from the central town of Thanh Loc, were among those traveling in the refrigerated container, according to Thanh Mien newspaper.
The family of Tra My, 26, released screenshots of what they say were her final messages to her mother.
"My journey abroad has not succeeded. Mum, I love you so much! I'm dying because I can't breathe," the message read.
According to her family, Tra My had worked in Japan for three years before leaving on October 3, bound for the UK via China and France.
Her father, Pham Van Thin, said her messages were sent in the early hours of Oct. 23, just before the bodies were discovered inside the truck.
Vietnam's ambassador to the UK, Tran Ngoc An, travelled to Grays on Saturday to meet with police and local officials, the British press reported.
In a statement, Detective Chief Inspector Martin Pasmore of Essex Police said he could not speculate on the nationality of the victims although confirmed police had been in touch with Vietnamese authorities.
"The investigation hasn't shifted anywhere. I've always remained completely open-minded as to which nationalities I may have as my victims," he said.
"Although we can't speculate at this time on the nationality of our victims, it's clear from everybody that we are getting a large amount of engagement from the Vietnamese population, from communities home and abroad," Pasmore said.
UK authorities are currently carrying out postmortem examination of the victims and do not plan to release any information until the process is complete.
Meanwhile, Polish authorities on Friday said they had stopped a lorry that was transporting 10 Vietnamese migrants.
The vehicle, stopped near the border with Lithuania, was being driven by a 44-year-old Polish national transporting wood.
( With inputs from IANS )