A truck with 39 bodies was found in Essex, southeast England. The driver, who is a 25-year-old man from Northern Ireland, was arrested.
"We have arrested the lorry driver in connection with the incident, who remains in police custody as our inquiries continue," Ch Supt Andrew Marine said.
Early indications are that 38 adults and one teenager have died, the force said, reported by BBC.
The victims are yet to be identified. Authorities believe the truck arrived from Bulgaria and entered the United Kingdom on October 19 through Holyhead, North Wales.