Throughout the day, prayers for the dead rang out over loudspeakers. Residents, their heads bowed, could be seen walking solemnly through Yen Thanh’s rain-soaked streets.

Situated in a remote stretch of Vietnam’s Nghe An province, Yen Thanh is where many of the 39 people found dead in the back of a lorry 6,000 miles away in Essex are believed to have started their tragic journey. The district now finds itself at the epicentre of a global police inquiry into the smuggling ring thought to be responsible for the UK’s biggest murder investigation since the 7/7 London bombings.

Facebook Twitter Pinterest Hoang Thi Thuong, wife of Nguyen Dinh Tu, a Vietnamese man suspected to be among the victims. Photograph: Nguyen Huy Kham/Reuters

One Catholic priest, Fr Anthony Dang Huu Nam, is among those who have started the macabre task of collating contact details for all the victims’ families. “The whole district is covered in sorrow,” Nam said. “This is a catastrophe for our community.”

On Saturday night, at the family house of Nguyen Dinh Tu in Phu Xuan, one of the people suspected to have died in the lorry, mourners streamed in and out all day to pay their respects. Inside the house, a dozen women sat on the floor on mats, their eyes red from crying.

Tu, the youngest of five brothers and sisters, left home for Europe in March, paying 70m dong (£2,350) to get to Romania, the Observer understands. After working in Romania for some months, he went to Germany and then decided to go to the UK, where his father in law lives, to earn more money.

Tu’s father-in-law helped him contact people smugglers who said they could help him get to England – for a cost of £11,000. He made it to France but his family said they lost contact with him on 22 October. That was the last they heard from him. “I haven’t heard anything from my son,” Nguyen Dinh Sat said.

Play Video 0:50 Vietnamese community leader says majority of lorry victims were probably from Vietnam - video

The scale of the tragedy emerged last Wednesday on a bleak industrial estate in Grays at 1.40am when a call was made to paramedics alerting them to a grisly discovery.

Yet, four days on, major gaps in our knowledge remain. How the 31 men and eight women came to be in the truck is not yet known. Neither is exactly where all of the victims came from. Police are still desperately trying to track down the driver who delivered the trailer to the Belgian port in Zeebrugge before it was ferried on Tuesday afternoon across the channel to Purfleet in Essex.

Belgian authorities have been tasked with “tracking the route of the container” and apprehending anyone responsible for “collaborating with the transport.” CCTV at Zeebrugge tracked the sought-after lorry as it arrived at the terminal with reports indicating it was filmed 10 times at the port.

On Saturday Dirk de Fauw, mayor of Bruges and chair of the port of Zeebrugge, confirmed no breakthrough had been made but was aware some of the suspected victims had been spotted in the country shortly before the tragedy.

Facebook Twitter Pinterest A relative looks at an image of Bui Thi Nhung. Photograph: Nguyen Huy Kham/Reuters

Among them was Vietnamese teenager Bui Thi Nhung, whose Facebook page showed her sightseeing in Brussels on 18 October, before she told friends she was making her way to France and onto the UK where she had relatives.

On 21 October, two days before the doomed truck was discovered, a friend asked the 19-year-old how her journey was going. “Almost spring,” Nhung responded, using a term in Vietnamese meaning she had almost reached her destination.

The teenager then went quiet. On Saturday dozens of worried relatives gathered in the family’s modest courtyard home where her distraught mother lies bedbound from anxiety.

“We are waiting and hoping it’s not her among the victims, but it’s very likely. We pray for her everyday. There were two people from my village travelling in that group,” said Hoang Thi Linh, Nhung’s cousin.

Despite an initial statement from Essex police that the 39 victims were Chinese, emerging evidence suggests it is increasingly likely that the majority of victims were from Vietnam.

Play Video 1:03 Essex lorry deaths: 'We cannot speculate about the nationality of the deceased,' say police – video

Essex police revealed on Saturday that detectives had met the Vietnamese ambassador and were “engaging” with the UK’s Vietnamese community to try to identify victims, though could not rule out other nationalities among the dead.

Previous similar tragedies suggest the identification process will take many more days. So far the only families to have gone public with their concerns about missing loved-ones are those of Pham Thi Tra My, a 26-year-old woman, and Nguyen Dinh Luong, 20.

On Friday the family of Pham revealed they had paid £30,000 for her to travel to the UK, but were increasingly fearful she was sealed inside the refrigerated container when she finally arrived. A sequence of messages stated: “I’m sorry Mum. My path abroad has not succeeded. Mum, I love you so much. I’m dying because I can’t breathe.”

Luong earlier this month told family that he planned to travel to Britain from France. His father has described receiving a call several days ago from a Vietnamese individual saying that “something unexpected happened”.

Facebook Twitter Pinterest Nguyen Dinh Luong and Pham Thi Tra are believed to have been among the victims. Photograph: Handout

In Phu Xuan, Tu’s family were in a state of agonising limbo, their relative’s death not official, but strongly feared. Tu’s wife, Hoang Thi Thuong, said she still owed money to the people smugglers who had offered to get him to Britain, although some reports yesterday said those responsible were handing out refunds to families of the dead.

“I have a big debt to pay, no hope, and no energy to do anything,” she told Reuters. Tu and Nhung had joined the huge numbers fleeing one of Vietnam’s poorest provinces. According to a recent report by the Pacific Links Foundation, a US-based anti-trafficking organisation, more victims are trafficked from Nghe An than anywhere else in Vietnam to be exploited in Europe.

“Nghe An is a top source province for labour or guest workers moving overseas,” said the report. Analysing the province’s demographics, it found 58% of the population – 1.8 million out of 3.1 million people – are eligible as “labour resources” and that many families in Nghe An have close relatives who work overseas, including a significant number of parents whose children are then left in the care of extended family

For those who remain in the town, located 180 miles south of Hanoi, it remains to be a seen whether last week’s tragedy will slow the exodus. For now, they can only pray. “I will hold a ceremony to pray for them tonight,” said Nam.