The truck, which is said to have entered the country on Saturday, was found by ambulance workers at Waterglade Industrial Park in Grays.
“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.”
Police have closed access to and from the industrial park.
“We are working with Thurrock Council to mitigate against any impact our investigation scene will have locally.” Mariner said.
When did this happen?
Emergency services rushed to Waterglade Industrial Park in Grays, at roughly 1:40 a.m. local time. Grays is about 20 miles east of London.
Have the bodies been identified?
All 39 people found were pronounced dead at the scene. Early indications suggest 38 are adults and one is a teenager.
“We are in the process of identifying the victims, however I anticipate that this could be a lengthy process,” Mariner said.
Is there a suspect?
A 25-year-old-man from Northern Ireland who is the truck’s driver has been arrested on suspicion of murder. He remains in custody.
Home Secretary Priti Patel tweeted: “Shocked & saddened by this utterly tragic incident in Grays. Essex Police has arrested an individual and we must give them the space to conduct their investigations.”