U.K. police have charged a truck driver with 39 counts of manslaughter and conspiracy to traffic people in the 39 people found dead in a truck container in southeastern England.

Authorities announced the charges Saturday against Maurice Robinson, 25, of Northern Ireland, who was arrested shortly after the grisly discovery of the bodies was made in southeastern England early Wednesday. He is due to appear in court Monday.

In addition to manslaughter and trafficking, he also faces charges for conspiracy to assist unlawful immigration and money laundering.

Authorities said earlier this week all of the 39 victims — 8 women and 31 men — were believed to be Chinese nationals, but at a news conference Saturday, authorities said they are not sure of their nationality.

Essex Police Detective Chief Inspector Martin Pasmore said that his officers had found “very, very few ID papers” among the bodies and appealed to anyone with information to come forward.

It is the largest mass fatality victim identification process in the history of Essex Police, authorities said.

"We don't know exactly the nationality of our individuals," Pasmore said. "But at the moment, I'm going to focus and engage as much as I possibly can within the Vietnamese community."

Pasmore said he met Saturday morning with the Vietnamese ambassador to Britain amid reports that many of the victims are from that Asian country.

"We are getting a large amount of engagement from the Vietnamese population, from communities home and abroad," Pasmore also said. "And I need to try and separate those."

In addition to Robinson, three other people have also been arrested on suspicion of human trafficking in the case, British police said Friday. A 38-year-old man and 38-year-old woman from Warrington and a 48 year-old man from Northern Ireland, who were arrested on suspicion of conspiracy to traffic people and manslaughter remain in custody.

U.K. authorities have been conducting a sprawling investigation into how the bodies came to be in a truck container southeastern England in what is one of the country's worst human-smuggling cases.