A murder investigation has been launched after 39 people were found dead inside a shipping container in Essex.
The bodies were discovered in the early hours of Wednesday morning at Waterglade Industrial Park, Eastern Avenue, Grays.
Essex Police say they were called by the ambulance service shortly before 1.40am on Wednesday following the discovery of a lorry container with people inside.
Early indications suggest that 38 adults and one person aged in their teens were found, police said. They were all pronounced dead at the scene.
A 25-year-old-man from Northern Ireland has been arrested on suspicion of murder.
The lorry is from Bulgaria and entered the UK at Holyhead in north Wales, one of the main ports for ferries from Ireland.
Experts have said the container appeared to be a refrigerated unit, where temperatures can be as low as -25C - and described conditions for anyone inside as "absolutely horrendous".
Chief Superintendent Andrew Mariner said: "This is a tragic incident where a large number of people have lost their lives. Our enquiries are ongoing to establish what has happened.
"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, October 19 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 enquiries 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."
At a press conference at Grays police station, deputy chief constable Pippa Mills said police were unable to identify the bodies.
She said: "Please appreciate we are in the early stages of what is likely to be a lengthy investigation.
"I'm unable to say at this stage how long the cordon will be in place.
"But please let me reassure you that my officers and partners will be doing everything they can to release the scene as soon as possible.
"This is an absolute tragedy and very sad day for Essex police and the community.
"We will continue to work alongside many other partner agencies to find out what led to these deaths.
"I would like to appeal to anyone who has any information to contact my officers at the major investigations team."
Haulage industry experts suggested the lorry was likely to have arrived in Ireland from Cherbourg or Roscoff, avoiding the tighter checks for people smuggling at Calais and Dover.
Footage from the scene in Thurrock showed forensic officers examining the lorry and its unmarked container.
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