The 39 people found dead in a truck container in Essex, east of London, are all believed to be Chinese nationals, local police have confirmed.

Key points: Police provided more details about the 39 victims, and earlier raided three properties in Northern Ireland

Police provided more details about the 39 victims, and earlier raided three properties in Northern Ireland The truck and the container came from separate places and only linked up before a final trip to the estate where the bodies were found

The truck and the container came from separate places and only linked up before a final trip to the estate where the bodies were found The driver, a 25-year-old from Northern Ireland named locally as Mo Robinson, remains in custody on suspicion of murder

On Thursday morning (local time), police conducted raids on three properties in County Armagh, Northern Ireland, in relation to the incident.

Police later confirmed all 39 of the victims were believed to be Chinese nationals. Eight of them were women and 31 were men.

Essex Police previously reported one of the victims was a teenager, but have since clarified she may have been "a young adult woman".

They said a 25-year-old man — locally identified on Wednesday as Mo Robinson from Northern Ireland, who was the driver of the truck — remains in custody on suspicion of murder.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 49 seconds 3 m 49 s The deadly routes and risks involved in people smuggling in Europe

Later on Thursday police confirmed they had been granted an additional 24 hours to hold the truck driver in custody.

Essex Police said in a statement: "Throughout yesterday, our detectives worked with partners to conduct initial enquiries into these tragic deaths and we continue to work diligently to piece together the circumstances of this horrific event, which has led to the largest murder investigation in our force's history.

"Our work continues today, and for the foreseeable future, to be focused on providing the victims and their loved ones with an investigation that is filled with dignity, compassion and respect for those who have died. "

The Chinese embassy in London said in a subsequent statement: "We read with a heavy heart the reports about the deaths of the 39 people in Essex.

"We are in close contact with the British police to seek clarification and confirmation."

The Chinese Foreign Ministry posted a statement on its social media account saying that Chinese embassy employees in the UK were driving to the scene of the crime to aid the investigation.

The bodies of the victims were discovered inside the truck container on an industrial site in Grays, in the early hours of Wednesday morning.

Police confirmed the truck had since been moved from the industrial park "to allow the next stage of [the] investigation to be conducted in peace, and to give the utmost dignity to those within the trailer as we prepare for a coroner's post-mortem examination".

They added each of the 39 bodies would undergo a "full coroner's process" to establish cause of death, before any of them were identified.

"This will be a substantial operation and at this stage we cannot estimate how long these procedures will take," Essex Police said.

The force also confirmed details of the truck's movements, saying the tractor unit of the truck entered the UK via Holyhead on October 20, having travelled over from Dublin.

The truck then collected the trailer, having travelled from Zeebrugge in Belgium, at the port of Purfleet at about 12:30am on October 23.

The cab and trailer then left the port shortly after 1:05am.

The truck was originally linked to Bulgaria, but Bulgarian Prime Minister Boyko Borissov said it had not been back there since 2017, when it was registered to a company owned by an Irish citizen.

"There is no connection with us, just the licence plates," Mr Borissov told national television.

Mr Robinson is not considered to be the owner of the truck.

The truck's driver, named as Maurice Robinson, is in custody and has been charged. ( Facebook: Mo Robinson )

UK Prime Minister Boris Johnson said he was appalled by the news and was receiving regular updates about the investigation, which was focused on human trafficking.

The National Crime Agency said it was assisting the investigation and working to "urgently identify and take action against any organised crime groups who have played a role in causing these deaths".

The discovery is among the worst of its kind in the UK.

The bodies of 58 Chinese people were found in a container at Dover, Kent, in 2000.

In 2015, the decomposing bodies of 71 people, including a baby girl, were found inside a truck on an Austrian motorway.

ABC/Wires