Residents of the English town of Grays, 20 miles east of London, said their hearts were “broken” after 39 people, including a teenager, were found dead in a truck at an industrial park Wednesday October 23rd, 2019.

Eastern Avenue, a street in the heart of the usually-bustling industrial area, was closed off after ambulance workers made the discovery and called police around 1:40 a.m.Police said the container arrived at a nearby town after traveling from the Belgian port city of Zeebrugge early Wednesday, before it was transported by the truck to Waterglade Industrial Park. Police have not yet identified the 39 victims or their nationalities, however a 25-year-old truck driver from Northern Ireland was arrested on suspicion of murder. Paul Berry, a local councilor for Armagh in Northern Ireland, identified the driver as Morris Robinson.

Essex Police Deputy Chief Constable Pippa Mills told reporters “number one priority” for police was finding out who the victims were and where they were from. The force set up a helpline for people to call if they are concerned their relatives might have been among those inside the truck. Aerial footage of the scene, filmed by Reuters, showed a police cordon and black tent set up at the back of the white container, which was attached to a red Scania truck.

The industrial estate where the truck was found is home to logistics and courier companies, some of which were inaccessible because of the cordon.

The truck was later moved, as seen by CNN, to a “secure location” at Tilbury Docks, about a 20-minute drive away from Grays, to “maintain the dignity of those who have lost their lives.”

A British Red Cross official at the scene told CNN it will assist in the identification process and offer support to families.

Richard Burnett, chief executive of trade body the Road Haulage Association, told reporters the container appeared to be refrigerated. That could mean freezing temperatures of anywhere between -5 to -10 degrees Fahrenheit, he told PA Media, making conditions “absolutely horrendous” for anyone stuck inside.

Irish, Northern Irish and Bulgarian authorities were alerted to the discovery as English forces scrambled to figure out the truck and container’s route to the United Kingdom. Earlier, police said the Bulgaria-registered vehicle entered the United Kingdom through the Welsh port of Holyhead over the weekend. A regular ferry service connects Holyhead with the Irish capital, Dublin. However, police later said the truck, and not the container, originated in Northern Ireland.

Bulgaria’s Ministry of Foreign Affairs said the Scania truck was registered in the Bulgarian coastal city of Varna by an Irish citizen. In a statement, it added that police think it’s “highly unlikely” the victims were Bulgarian citizens. Bulgarian Prime Minister Boyko Borissov told local broadcaster the truck was registered in the country in 2017 but left and never re-entered.

Irish Prime Minister Leo Varadkar told the country’s Parliament that investigations would be carried out “if it’s established the truck passed through Ireland.” Ireland’s police force, An Garda Síochána, said it was monitoring the UK investigation “and will provide every assistance possible.”

Human trafficking incidents

In recent years there have been a number of fatal incidents in the United Kingdom and Europe involving large numbers of migrants who were found suffocated to death in trucks or containers. Four human traffickers were given life sentences this summer over the deaths of 71 migrants whose bodies were found in an abandoned truck in Austria in 2015, Reuters reported.In 2000, 58 Chinese migrants were found dead in a lorry in Dover.

The past year has seen an increase in the number of migrants attempting to cross the English Channel by boat. Experts have partially linked that rise to the United Kingdom enforcing more stringent border checks — which in turn has made the option of truck crossings a more difficult and costly affair, as smugglers raise their fees.

The suspects: Mo Robinson, a 25-year-old Northern Irish truck driver, was arrested Wednesday on suspicion of murder. On Friday, police arrested three more suspects — a 48-year-old man from Northern Ireland, and a man and a woman, both 38. They were arrested on suspicion of manslaughter and trafficking-related offenses.

Autopsies have started on some of the victims as police work to identify them. Police have said the eight women and 31 men inside the truck were Chinese. However, China contests the claims, saying it is “not yet possible” to confirm the victims’ nationalities.

Mills added police would give no more information on the nationalities of the victims until formal identification had been completed.