A fourth person was arrested in connection to the deaths of 39 people inside the back of a semitruck in southeast England, as new reports emerged claiming some of the victims may have been Vietnamese.

Essex police said Friday that a 48-year-old man from Northern Ireland was arrested at Stansted Airport on suspicion of conspiracy to traffic people and on suspicion of manslaughter.

The news of the arrests follows the detention of two other people – a man and a woman, both 38, of Warrington – earlier Friday. They were arrested on the same charges.

“This is a fast-moving investigation involving significant police resources dedicated to finding out the truth about what happened to the 39 people found dead in the lorry on Wednesday,” Deputy Chief Constable Pippa Mills said in a statement.

CHINESE PAPER SAYS BRITAIN SHOULD HAVE DONE MORE TO PREVENT DEATHS INSIDE TRUCK

The bodies of 31 men and 8 women were found inside the truck container early Wednesday at the Waterglade Industrial Park in Grays, a town about 25 miles east of London.

The driver, a 25-year-old man from Northern Ireland, was arrested on suspicion of murder. He remains in custody on Friday.

Officials said the remains of 11 people from the truck were transported by ambulance from the Port of Tilbury under police escort on Thursday. The first autopsies to determine the cause of death are expected to begin Friday.

“This process is likely to be a lengthy one, but it is crucial, and we’re working with Her Majesty’s Coroner to ensure the dignity of the victims and the respect for their loved ones is at the forefront of our investigation,” Mills said. “I’m acutely aware of the international interest in this case and the appetite for information.”

CHINESE PAPER SAYS BRITAIN SHOULD HAVE DONE MORE TO PREVENT DEATHS INSIDE TRUCK

British police had initially identified the victims as Chinese nationals, but a statement earlier Friday appeared to move away from the initial reports, saying that the “picture may change regarding identification.”

Chinese officials told reporters in Beijing the nationalities and identities of the victims had not yet been confirmed.

British media have reported that several Vietnamese families have contacted authorities with fears that their relatives may have been among the dead.

At least six of the victims may have been Vietnamese, according to the BBC, with one family saying a woman – identified as Pham Thi Tra My, 26 – has not been heard from since allegedly sending text messages saying she could not breathe.

Her brother told the BBC that she had paid more than $38,000 to human smugglers and that her last-known location had been Belgium.

The Vietnamese Embassy in London confirmed Friday that it contacted police about a missing woman feared to be one of the dead. An embassy spokesman said it was contacted by a family in Vietnam who says their daughter had been missing since the truck was found.

Chinese Foreign Ministry spokeswoman Hua Chunying said China was working in cooperation with local authorities.

"No matter where these victims come from, this is a great tragedy which drew the attention of the international community to the issue of illegal immigration," she said. "The international community should further strengthen cooperation in this area, strengthen sharing of information and intelligence ... to prevent such tragedies from happening again."

Essex police said it would not comment on speculation regarding the nationalities of the victims.

39 FOUND DEAD IN TRUCK ENGLAND WERE CHINESE NATIONALS: POLICE

The truck left the Belgian port via ferry and headed to Purfleet, England, where it arrived early Wednesday. Its location before then remains unclear.

As for the tractor unit of the truck – the smaller section at the front of the vehicle, police said it began its journey in Northern Ireland, where it made its way to Dublin. There it caught a ferry to Holyhead in north Wales before making its way to Essex. It picked up the container around 12:30 a.m. Wednesday in Thurrock.

TRUCK WITH 39 BODIES ENTERED ENGLAND FROM BELGIUM VIA FERRY, POLICE SAY AS NEW DETAILS EMERGE

It departed the dock around 1:05 a.m. and was spotted in CCTV footage going toward the industrial park just minutes before the bodies were discovered inside.

“This is the largest investigation of its kind Essex Police has ever had to conduct and it is likely to take some considerable time to come to a conclusion,” Chief Constable Ben-Julian Harrington said in a statement.

The tractor unit is registered in Bulgaria to a company owned by an Irish woman.

Global Trailer Rentals Ltd told Ireland's national broadcaster RTE the trailer it owns was leased Oct. 15 in County Monaghan, in Ireland, at a rate of 275 euros ($299) per week. The Dublin-based company said it will make the data from its tracking system available to investigators.

The company's directors told RTE it was "shell-shocked" at the news.

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Three addresses in County Armagh were searched following the arrest of the driver.

The tragedy recalls the deaths of 58 Chinese migrants who suffocated in a truck in Dover, England, in 2000 after a perilous, months-long journey from China's southern Fujian province. They were found stowed with a cargo of tomatoes after a ferry ride from Zeebrugge, the same Belgian port that featured in the latest tragedy.

In February 2004, 21 Chinese migrants — also from Fujian — who were working as cockle-pickers in Britain drowned when they were caught by treacherous tides in Morecambe Bay in northwest England.

The Associated Press contributed to this report.