LONDON -- British police arrested a 23-year-old man from Northern Ireland on Friday over the deaths of 39 people from Vietnam whose bodies were found in a refrigerated container truck last month.

The Essex Police force said the man was detained on a highway northwest of London on suspicion of conspiracy to traffic people and conspiracy to assist unlawful immigration.

The bodies were found Oct. 23 in the English town of Grays. Police say the victims were all from Vietnam and aged 15 to 44.

The 31 men and eight women are believed to have paid people traffickers for their clandestine transit into England.

British police have already charged 25-year-old Maurice Robinson, a truck driver also from Northern Ireland, with 39 counts of manslaughter and conspiracy to traffic people. They say he drove the cab of the truck to Purfleet, England, where it picked up the container, which had arrived by ferry from Zeebrugge in Belgium.

In Ireland, 22-year-old Eamonn Harrison faces U.K. extradition proceedings on charges of manslaughter. Several other people have been arrested in Vietnam.