Grays, England (CNN) 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.

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. Berry told CNN he learned of the arrest after speaking with Robinson's father.

Morris Robinson was identified by a councilor in Northern Ireland as the driver of the truck that was found with 39 people dead.

The local councilor said the driver was known locally as "Mo," and that his family is "salt of the earth and clearly we need to give them space."

Wednesday, Essex Police Deputy Chief Constable Pippa Mills told reporters the "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.

Police say a 25-year-old Northern Irish truck driver has been arrested "on suspicion of murder."

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

Dan Peters, a managing director of Pirtek, a hydraulic maintenance company based on the street where the truck was found, told PA news agency they were not able to open for business Wednesday.

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."

British Red Cross to help identify victims

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

"I can't overstate how big a tragedy it is that 39 people felt like they had no better option than to get in the back of this truck and obviously it's ended in an absolute tragedy," said Matthew Carter, an emergency communications delegate for the British Red Cross.

Matthew Carter from the British Red Cross, standing near where the truck was found, said the charity is helping both families and emergency workers.

He added the charity was also giving support to the forensic team, offering them "somewhere where they can come and reflect, have a chat."

"It's not something (emergency services) deal with on a day-to-day basis," Carter told CNN. "One chap told a colleague of mine that it's the hardest thing that he's dealt with in (his) 30-year-career."

Grays resident Shafi Said, who lives one street away from the industrial estate where the truck was found, told CNN his heart was broken for the 39 people who died.

"It's so sad. My heart is broken for them," Said told CNN. "They're all innocent people -- and there was a child on board. I've got an 11-year-old son. I was so shocked."

Shafi Said, who moved to Essex from Afghanistan in 2001, told CNN he is heartbroken at the news.

The 35-year-old taxi driver moved to the area almost 20 years ago to escape the war in Afghanistan. He said his wife and three children were happy in Grays, which he described as "multicultural" where trucks are "always passing by."

PM 'appalled' by tragedy

News of the grisly discovery shocked British lawmakers; many members of Parliament speculated in the House of Commons on Wednesday that the incident was linked to human trafficking. Police have not confirmed that claim.

As the tragedy unfolded, UK Prime Minister Boris Johnson called for the perpetrators and "all such traders in human beings" to be "hunted down and brought to justice."

Jackie Doyle-Price, the member of Parliament for Thurrock, where the bodies were found, wrote on Twitter: "Sickening news of 39 people found dead in a container in Grays. People trafficking is a vile and dangerous business. This is a big investigation for @EssexPoliceUK Let's hope they bring these murderers to justice."

Sickening news of 39 people found dead in a container in Grays. People trafficking is a vile and dangerous business. This is a big investigation for @EssexPoliceUK Lets hope they bring these murderers to justice — Jackie Doyle-Price (@JackieDP) October 23, 2019

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.

Joint investigation

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.

"We have arrested the lorry driver in connection with the incident who remains in police custody as our enquiries continue," Chief Superintendent Andrew Mariner of Essex Police said in a statement.

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 bTV the truck was registered in the country in 2017 but left and never re-entered.

"There is no way that we can be connected except for the registration plate of the truck. Despite this, we are working very well with the British authorities," Borissov said.

Police say the truck is registered in Bulgaria.

Irish Prime Minister Leo Varadkar told the country's Parliament on Wednesday 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.

Flowers were laid at the entrance to the industrial park in Grays, Essex, where 39 bodies were found inside a truck container.

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 UK has invested a lot of money in protecting the lorry routes" from migrants crossing from France, Nando Sigona, an associate professor in international migration at the University of Birmingham, told CNN earlier this year. "That route has probably been sealed off, or made more difficult to pursue."

This story has been updated to correct the time police were called by the ambulance service.