Police have arrested a fourth person following the discovery of 39 bodies in a lorry in Essex.
Deputy Chief Constable Pippa Mills, of Essex Police, said a 48-year-old man was arrested at Stansted Airport on suspicion of conspiracy to traffic people and manslaughter.
It follows the arrest of a 38-year-old man and a 38-year-old woman from Warrington.
A 25-year-old man from Northern Ireland, named locally as Mo Robinson, remains in custody, police said.
Ms Mills said she would not be drawn on any further detail about the nationality of the victims until formal identification processes had taken place.
“I strongly urge journalists and people on social media not to speculate about the identities of those involved or the circumstances surrounding this investigation,” she said.
“We gave an initial steer on Thursday on nationality, however this is now a developing picture.”
Ms Mills said: “I can confirm we have officers working around the clock and we have now arrested a fourth person.
“A 48-year-old man from Northern Ireland was arrested at Stansted Airport earlier today on suspicion of conspiracy to traffic people and on suspicion of manslaughter.
“It follows the arrests of a 38 year-old man and a 38 year-old woman from Warrington during warrants executed in Cheshire overnight. They are currently in custody also on suspicion of conspiracy to traffic people and on suspicion of manslaughter.
“A 25-year-old man arrested on Wednesday on suspicion of murder remains in custody.
“We are working closely with the National Crime Agency, the Home Office, the Foreign and Commonwealth Office, Border Force and Immigration Enforcement.”
Meanwhile, Liu Xiaoming, the Chinese Ambassador to the UK, said in a tweet: “Latest report from the Minister-Counsellor of my Embassy: Essex police emphasised they are still verifying the identity of the 39 deceased.
“We are waiting for the police to identify the victims. This is a number one priority.”
Earlier: Arrested couple originally from Ireland
The driver of the lorry which contained the bodies of 39 migrants is due to appear in court tomorrow.
Mo Robinson, from Portadown, Co Armagh is due at Chelmsford Magistrates’ Court in England tomorrow morning, a crown court official has said.
It comes as a man and a woman, originally from Ireland and both aged 38, were arrested in connection with the investigation today.
Joanna and Thomas Maher, with an address in Warrington, England, claimed yesterday they had sold the Scania lorry cab, which is registered in Bulgaria, to a company in Ireland.
Mrs Maher, who is reportedly the last known owner of the vehicle, told MailOnline: “We did own it but sold it 13 months ago.”
Police officers could be seen at the couple’s home address in Warrington, with a police van and two squad cars parked outside.
Officers carried evidence bags inside the four-bedroom property, which had two grey Range Rovers with personalised number plates and a white Chevrolet sports car parked on the drive.
The house was bought by the couple, originally from Ireland, for £255,000 in March 2017, according to Land Registry records, before the couple undertook extensive renovations on the property, according to neighbours.
Locals said Mr Maher is the owner of a haulage firm and his wife works as a hairdresser. They said they have three teenage children.
A neighbour, who did not want to be named, said: “I’m absolutely stunned. My wife got up about 20 past seven, saw the police cars already here.
I was shocked...I could not believe it.
Nodding towards the cars parked on the drive, he added: “I know Tom is a businessman, a successful one, in haulage. Tom and Jo are very pleasant, very approachable. A guy with a family, you couldn’t meet more well-mannered children.
“You would see them walking their dogs and they would go to boxing matches, his daughter liked boxing.”
Mr Maher was listed as director of Thomas Maher Transport Ltd, but according to Companies House records, ceased to be a person with a significant interest in the firm on February 7.