The Vietnam government has said it “strongly condemns” human trafficking, after British police confirmed 39 people found dead in a truck last week are believed to be Vietnamese, describing it as a “serious humanitarian tragedy”.

Essex police announced on Friday that they believed they knew the nationality of all the victims, having previously suggested that some were of Chinese heritage when the bodies were discovered on 23 October.

Eight women and 31 men were discovered in a refrigerated trailer attached to a lorry in an industrial park in Grays.

Le Thi Thu Hang, a spokeswoman for Vietnam’s ministry of foreign affairs, said the government was deeply saddened by the incident and wished to extend its heartfelt condolences to the victims’ families.

She said the Vietnamese embassy in the UK had been working closely with the British authorities to support families and help identify the victims.

Hang said: “Vietnam strongly condemns human trafficking and considers it a serious crime subject to strict penalties.

“Vietnam calls upon countries in the region and around the world to step up cooperation in combating human trafficking in order to prevent the recurrence of such tragedy.

“We are grateful that the British government and other relevant authorities have actively conducted the investigation [and] provided identification information and worked in close coordination with the Vietnamese competent authorities.

“We hope that the British side [will] soon complete the investigation to bring those responsible for this tragedy to justice.”

Assistant chief constable Tim Smith said the force was in direct contact with a number of families in Vietnam and the UK and believed it had identified families for some of the victims.

He said the force was awaiting “confirmatory evidence” in order to present the case to the coroner.

Smith added: “This evidence is being gathered across a number of jurisdictions worldwide. As a result, we cannot at this time announce the identity of any of the victims.”

Essex police have initiated extradition proceedings to bring suspect Eamonn Harrison, 22, from Ireland to the UK.

Harrison, of Newry in County Down, Northern Ireland, appeared in Dublin high court on Friday charged with 39 counts of manslaughter, along with human trafficking and immigration offences, and was remanded in custody.

Detectives have also urged Ronan Hughes, 40, and his brother Christopher, 34, said to have links with the road haulage and shipping industries, to hand themselves in.

The pair, from Armagh in Northern Ireland, are wanted on suspicion of manslaughter and human trafficking.

It is understood Ronan Hughes spoke to police shortly after the driver of the lorry, Mo Robinson, 25, was arrested following the discovery.

Robinson, of Craigavon, Northern Ireland, appeared at Chelmsford magistrates court on Monday charged with 39 counts of manslaughter, conspiracy to traffic people, conspiracy to assist unlawful immigration and money laundering.

Three other people arrested in connection with the incident – two men aged 38 and 46, and a 38-year-old woman – have been released on bail.

In Vietnam, local media reported that police in Ha Tinh province had arrested two people in connection with the deaths after launching an investigation into suspected human trafficking of workers.

It is still not known how the victims entered the lorry trailer before it travelled from Zeebrugge in Belgium to Purfleet in Essex.