British police have arrested a man on suspicion of murder after the bodies of 39 people were found in a truck container at an industrial estate east of London.
The victims, found at the Waterglade Industrial Park in Grays, Essex, on Wednesday included one teenager, police say.
A 25-year-old man from Northern Ireland has been arrested on suspicion of murder.
Early indications suggest there 38 are adults and one teenager, police say.
The lorry is from Bulgaria and entered the country at Holyhead, North Wales, one of the main port for ferries from Ireland.
"This is a tragic incident where a large number of people have lost their lives. Our enquiries are ongoing to establish what has happened," Chief Superintendent Andrew Mariner said.
"We are in the process of identifying the victims. However, I anticipate that this could be a lengthy process.
"We believe the lorry is from Bulgaria and entered the country at Holyhead on Saturday, 19 October, and we are working closely with our partners to investigate.
"We have arrested the lorry driver in connection with the incident who remains in police custody as our inquiries continue.
"I appreciate this cordon is going to disrupt the activity of local businesses in the area and we will work to ensure that disruption is kept as short as possible.
"We are working with Thurrock Council to mitigate against any impact our investigation scene will have locally."
Australian Associated Press