UK police have charged a truck driver with 39 counts of manslaughter and conspiracy to traffic people in connection with 39 deaths in the back of the truck he was driving in southeastern England.

Police say Maurice Robinson, 25, of Craigavon, Northern Ireland is due to appear at Chelmsford Magistrates Court on Monday. He was the first of those arrested to be charged in what is seen as one of the UK's biggest cases of people smuggling. Four others have been arrested in the case.

UK police are struggling to identify the victims, who are believed to have come from Asia, and autopsies are being performed. The Vietnamese Embassy in London has set up a hotline for families to call about missing family members.

Maurice Robinson has been charged. (Photo / Facebook)

All of the 39 victims are now out of the truck and in a mortuary awaiting autopsies.

But Detective Chief Inspector Martin Pasmore says the victims have not been identified and very few documents were found with the bodies.

He met Saturday with the Vietnamese ambassador amid reports on social media that many of the victims were from that southeast Asian country.

Pasmore again appealed to those who might have information on the victims to help with inquiries.

Pham Thi Tra My's family fear she may have died in the Essex truck deaths. Photo / Family of Pham Tra My

'I am dying, I can't breathe.'

Vietnamese national Pham Thi Tra My, 26, texted her parents just hours before the grisly discovery was made saying she was struggling to breathe and her trip abroad had failed, according to her brother Pham Ngoc Tuan who spoke to the BBC.

"I am really, really sorry, Mum and Dad, my trip to a foreign land has failed," the translated texts said.

"I am dying, I can't breathe. I love you very much Mum and Dad. I am sorry, Mother."

Tuan had paid £30,000 (NZ$60,600) to be smuggled into the UK and her last-known location was Belgium, the BBC reported.

Nguyen Dinh Luong, 20, may be among the 39 people found dead in the back of the truck. Photo / AP

The father of 20-year-old Nguyen Dình Luong fears his son is among the dead. He told The Associated Press he hadn't been able to reach his son since last week, when the young man told his father he planned to join a group in Paris that was trying to reach England.

"He often called home, but I haven't been able to reach him since the last time we talked last week," Nguyen Dình Gia said. "I told him that he could go to anywhere he wants as long as it's safe. He shouldn't be worried about money, I'll take care of it."

His older brother, Pham Dình Hai, said Luong had a tattoo of praying hands on a cross on his right shoulder. The family said they shared the information with local authorities.

Essex residents have described the area where the truck container was found as rife with brazen people-smuggling operations that police have failed to act on.

Gary Lilley, 61, who lives opposite the Purfleet port where a container entered the UK this week that was found to have the bodies of eight women and 31 men sealed inside, said he had seen women and children wandering the streets after dark with carrier bags containing their belongings.

"I've lived here for 30 years and the situation is an absolute joke. I've seen literally hundreds of migrants smuggled into the country through the port," he told The Times.

"I worked there while in between jobs and it was chaos."