A man from Northern Ireland has been detained in connection with the deaths of 39 people found in the back of a container truck in southeastern England, British police said on Friday, bringing the total number arrested to four. The 48-year-old man was picked up at England’s Stansted Airport on suspicion of manslaughter and conspiracy to traffic people. A man and a woman, both 38 and from northwestern England, were arrested earlier on Friday on the same charges, while the 25-year-old truck driver, earlier identified as Mo Robinson, remains in custody on suspicion of murder. The new arrests came as police began the grim process on Friday of conducting postmortem examinations of the dead. The remains of 11 people from the truck were transported by ambulance on Thursday from the Port of Tilbury to a mortuary under police escort. Although British police said they believed all the victims – 38 adults and one teenager – were Chinese citizens, Chinese officials told reporters in Beijing the nationalities and identities of the deceased had not yet been confirmed. The Vietnamese embassy in London confirmed on Friday that it had contacted police about a missing woman feared to be among the victims. An embassy spokesman said it was contacted by a family in Vietnam who says their daughter had been missing since the truck was found. China has urged British police to speed up their investigation into the deaths, in a case that has been described as the worst human smuggling incident in Britain for nearly two decades. Foreign ministry spokeswoman Hua Chunying said in Beijing that the Chinese government “attached great importance” to the case and was coordinating its various departments to work with the British authorities. “We hope the British side will verify and confirm the identity of the victims as soon as possible, find out the truth of the incident … [and] seriously deal with the criminals who are responsible,” she said. Vietnamese woman feared to be among UK truck victims Police made the gruesome discovery at an industrial estate in Essex. The trailer is thought to have travelled to Britain via Belgium, while the tractor unit – the front part of the truck – that hauled it to the industrial estate is believed to have started its journey in Northern Ireland. British Prime Minister Boris Johnson described it as an “unimaginable tragedy”. Meanwhile, Global Times , a nationalist Chinese newspaper affiliated with Communist Party mouthpiece People’s Daily , said the British should be held responsible for the deaths. “Although these Chinese nationals appeared to have entered Britain in an improper way, it has yet been confirmed to what extent that they should be held responsible for this tragedy,” it said in a commentary. “However, such a serious humanitarian tragedy happened under the watch of British and European people, and it is clear that the UK and the relevant European countries have not fulfilled their responsibility in protecting these people. “China has put a lot of effort into protecting overseas Chinese, and we hope the UK and European countries can uphold their promises on [protecting] human rights,” it said, adding that European countries should do more to highlight the dangers of human smuggling. Shi Yinhong, a professor of international relations at Renmin University in Beijing, said illegal immigration from China was “commonplace”. “China’s economy has developed rapidly in recent years, but there are growing income differences,” he said. “Some people always think that there will be better employment opportunities abroad, and they don’t know anything about the status of illegal immigrants.” Lorry horror highlights risks migrants take to reach UK The Chinese embassy in London issued a statement on Friday saying a team led by the minister-counsellor in charge of consular affairs had been sent to Essex to liaise with police on the case. Hua said the tragedy underscored the importance of nations working together to prevent human trafficking . “Regardless of the nationality of the victims, this is a big tragedy. It has drawn the attention of the international community to the problem of people smuggling,” she said. “I hope the international community will step up cooperation in this area and strengthen intelligence sharing, take early steps to stop the problems from happening at their source, so tragedies like this do not happen again.” The incident is the worst of its kind in Britain since the bodies of 58 Chinese people were found in a container in Dover, Kent, in 2000. Two people survived that ordeal, and the Dutch truck driver was jailed for 14 years for manslaughter the next year. Additional reporting by Jun Mai, Agence France-Presse and Associated Press