The 39 people found dead in the back of a lorry in Essex were all Chinese nationals, it has been reported.
Police have searched two addresses in Northern Ireland connected to the driver - 25-year-old Mo Robinson from Northern Ireland, as the National Crime Agency works towards identifying "organised crime groups who may have played a part".
He remains in custody for questioning on "suspicion of murder".
It comes as Belgian authorities continue to investigate the journey of the lorry where the bodies were found.

Britain working with allies to support shipping through Strait of Hormuz
Five Iranian women's soccer players granted humanitarian visas in Australia
Almost 700,000 displaced after Israeli strikes on Lebanon, UN agencies say
Iran fighting back but not stronger than U.S. thought, top U.S. general says
British warship HMS Dragon departs for Eastern Mediterranean