Vietnam says it is trying to speed up the identification of citizens suspected to have been among the 39 found dead in a truck near London last week.
"The nationality of the victims hasn't been officially confirmed yet," Deputy Foreign Minister Nguyen Quoc Cuong told Reuters on Tuesday.
Vietnam and Britain "are trying to speed up identification of the bodies, but no deadline has been set," he said.
The truck's driver is facing charges of manslaughter and people trafficking. Maurice Robinson, 25, from Northern Ireland, appeared in court on Monday charged with 39 counts of manslaughter and other offences, including conspiracy to traffic people, after the bodies were found last week in Grays, about 20 miles east of London.
British police have sent documents regarding four of the victims to Hanoi for further verification.
On Tuesday, detectives named two suspects they want to speak to on suspicion of manslaughter and human trafficking – Ronan Hughes, 40, and his brother Christopher, 34, both from Armagh.
"Finding and speaking to the Hughes brothers is crucial to our investigation," said Detective Chief Superintendant Stuart Hooper.
The discovery of the bodies has shone a spotlight on an illicit trade that sends the poor of Asia, Africa and the Middle East on perilous journeys to the West
In Vietnam, poor job prospects, encouragement by authorities, smuggling gangs and environmental disasters are all local factors behind the wave of migrants.
The desire to go overseas has created a thriving underground market in the Southeast Asian country for people smugglers, many of whom promise safe and even "VIP" packages for secret travel to Europe, anti-trafficking experts, migrants and their family members have told Reuters.
News of the truck tragedy has plunged the rural provinces of Nghe An and Ha Tinh in northern-central Vietnam into despair, with many families fearing loved ones may be among the dead.
Police break up ceremony
Authorities in Nghe An have launched an appeal for concerned family members to submit copies of photos and identification of the missing to their local People's Committee for verification, according to a copy of the appeal seen by Reuters.
Vietnam's foreign ministry has so far received information from 14 concerned families seeking missing family members in the UK, the ministry said in a statement late on Monday.
Communist-ruled Vietnam is extremely sensitive to events that could lead to social unrest or public gatherings.
A candlelit ceremony outside a Catholic cathedral in Hanoi in memory of the 39 victims was broken up by police on Sunday, organisers said.