British police arrested two more suspects on Friday in connection with the deaths of 39 people found in the back of a container truck in southeastern England as the investigation into one of the country’s worst human smuggling cases geared up.

Police said the man and the woman, both 38 and from Warrington, a town in northwestern England, were arrested on suspicion of manslaughter and conspiracy to traffic people. The 25-year-old driver of the truck remains in custody on suspicion of murder.

The new arrests came as police began the grim process of conducting post-mortem examinations of the dead. The remains of 11 people from the truck were transported by ambulance from the Port of Tilbury to a mortuary under police escort on Thursday, and the post-mortems were to begin on Friday.

Meanwhile, Vietnam’s embassy in London said on Friday it had received requests from Vietnamese families asking for help in finding out whether their relatives were among the 39 victims found dead in the back of a truck near London.

“The embassy has not yet received any official confirmation from the British relevant agencies,” it added in a statement.

“The embassy has continued to follow the event and worked closely with relevant British agencies to accelerate the investigation process.”

A Vietnamese man said he fears his sister is among 39 people found dead.

The brother of 26-year-old Vietnamese woman Pham Thi Tra My said he thinks his sister was among the group. “We received information that My was among the 39 victims,” Pham Manh Cuong told AFP on Friday from central Vietnam. My left Vietnam on Oct.3 en route to the United Kingdom.

Cuong said their mother received a text message from My on Wednesday at 4:28am Vietnam time.

“I’m sorry Mom. My path to abroad doesn’t succeed. Mom, I love you so much! I’m dying bcoz I can’t breath,” she said in the message shared by the Vietnam-based Human Rights Space.

Her brother confirmed to AFP the text massage was authentic.

A Vietnamese security source told AFP on Friday: “There is a possibility there might be Vietnamese among the victims.” “We are working very closely with relevant agencies both in Vietnam and especially in the UK,” he added, speaking on condition of anonymity.

Although UK police said they believed the dead were Chinese citizens, Chinese officials told reporters in Beijing that the nationalities and identities of the victims had not yet been confirmed.

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.”

Hua said Chinese authorities were also seeking information from police in Belgium, since the shipping container in which the bodies were found was sent to England from the Belgian port of Zeebrugge.

Human smuggling from China is believed to have fallen drastically in recent years amid the country’s rapidly growing domestic economy. However, some Chinese, particularly those with lesser education, continue to be drawn to Europe and North America by the promise of much higher wages than they can earn at home, despite the considerable risks involved.

Parts of China, especially the southeastern province of Fujian, have long histories of sending migrants abroad.

The issue is a difficult one for China’s ruling Communist Party, which is intensely sensitive about China’s international image and has staked much of its legitimacy to rule on improving living standards for the bulk of China’s 1.4 billion people.

In an editorial Friday, the party newspaper Global Times said authorities in Britain and elsewhere hadn’t done enough to crack down on people smuggling.

Agencies