Authorities in the U.K. are searching for two brothers wanted in connection with the 39 dead bodies that were found in the back of a tractor-trailer near London last week.
Ronan Hughes, 40, and Christopher Hughes, 34, both from Armagh in Northern Ireland, are wanted on suspicion of manslaughter and human trafficking, Essex police said in a statement.
"Finding and speaking to the Hughes brothers is crucial to our investigation," said Stuart Hooper, the detective chief superintendent who is leading the investigation.
Authorities believe the pair are in Northern Ireland but also have links to the Irish Republic.
"This is a case where 39 men and women have tragically died and support from the community is going to be vital to help bring those responsible to justice," Hooper said.
A 25-year-old man has already been charged in connection with the case and appeared in court via video link on Monday.
Maurice Robinson, who is from Northern Ireland, is charged with 39 counts of manslaughter, conspiracy to traffic people, conspiracy to assist unlawful immigration, and money laundering. Prosecutors alleged he was part of "a global ring" involving "the movement of a large number of illegal immigrants into the U.K."
Robinson, who was arrested last Wednesday and identified by police as the driver of the truck, was not asked to indicate pleas and is next scheduled to appear in court on Nov. 25.
Three other suspects, two men and a woman, were also arrested last week and questioned on suspicion of manslaughter and conspiracy to traffic people, but they have not been charged. Two were released on bail until Nov. 11 and the third has been bailed until Nov. 13, according to Essex police.
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Emergency services were called to an industrial park in the town of Grays in Essex, southeast England, at around 1:40 a.m. local time on Oct. 23 when the vehicle was discovered to have people inside. Thirty-nine people -- eight women and 31 men -- were pronounced dead at the scene, which was about 20 miles east of London.