Police investigating the Manchester Arena bomb attack have temporarily stopped sharing information with the US after leaks to the media, the BBC understands.
UK officials were outraged when photos appearing to show debris from the attack appeared in the New York Times.
It came after the name of bomber Salman Abedi was leaked to US media 24 hours after the attack, which killed 22 - including children - and injured 64.
Theresa May is to raise concerns with Donald Trump at a NATO meeting later.
Greater Manchester Police hopes to resume normal intelligence relationships - a two-way flow of information - soon but is currently "furious", the BBC understands.
In total eight men are now in custody following the attack, carried out by Manchester-born Abedi, a 22-year-old from a family of Libyan origin.
It has also emerged two people who had known Abedi at college made separate calls to a hotline to warn the police about his extremist views.
Pictures of debris
Home Secretary Amber Rudd had said she was "irritated" by the disclosure of Abedi's identity against the UK's wishes and had warned Washington "it should not happen again".
However, the pictures of debris - which appear to show bloodstained fragments from the bomb and the backpack used to conceal it - were subsequently leaked to the New York Times, prompting a furious response from within Whitehall and from UK police chiefs.
BBC security correspondent Gordon Corera says UK officials believe that US law enforcement rather than the White House is the likely culprit for the leaks.
A Whitehall source described the second US leak as "on another level", and told the BBC it had caused "disbelief and astonishment" across the British government.
The source said the the issue was "being raised at every relevant level by the British authorities with their US counterparts".
The UK's National Police Chiefs' Council described the "unauthorised disclosure" as a breach of trust which had potentially undermined a "major counter-terrorism investigation".
Counter-terrorism detectives have spoken in the past about how important it sometimes is that the names of suspects do not make it into the media.
A delay of about 36 hours, before the public know who police are investigating, can allow known associates of the suspect to be arrested before they know police are looking for them.
Greater Manchester Mayor Andy Burnham said the leaks had worried him "greatly", and he had raised them with the US ambassador.
Further two arrests
The meeting between Mrs May and Mr Trump, at a NATO summit in Brussels, will take place as British police continue to investigate an alleged "network" linked to Abedi.
Early on Thursday morning, detectives carried out a controlled explosion as they searched a property in the Moss Side area of Manchester.
Two men were also arrested following a search of an address in the Withington area of Greater Manchester.
In total, eight men, including Abedi's older brother, and a woman have been arrested in a series of raids across Manchester, Wigan and Nuneaton.
The woman was subsequently released without charge in the early hours of Thursday.
Meanwhile, Abedi's father and a younger brother have been detained by militia in Libya.
In other developments, the government has announced that a minute's silence will be held at 11am British time on Thursday in remembrance of those who lost their lives or were affected by the attack.
The Conservatives and Labour are to resume local general election campaigning on Thursday, and national campaigning on Friday.
What's happening with the investigation?
Eight men and one woman have been arrested in the UK since Monday night, including Abedi's older brother Ismail, 23, although the woman has since been released.
Younger brother Hashem, 20, was held by militia in the Libyan capital Tripoli, as was their father.
Speaking on Wednesday afternoon, Greater Manchester Chief Constable Ian Hopkins said: "I think it's very clear that this is a network that we are investigating.
"And as I've said, it continues at a pace. There's extensive investigations going on and activity taking place across Greater Manchester, as we speak."
As part of their investigation, police raided a block of flats near Manchester Piccadilly station in the city centre, requiring them to carry out a controlled explosion and briefly close the railway line.
Police carried out another controlled explosion in the early hours of Thursday morning at an address in the Moss Side area of Manchester.
Who are the victims?
Some of the victims had been making their way outside at the end of the Ariana Grande gig when Abedi detonated his "nuts-and-bolts" bomb.
They include children and teenagers and others who had been waiting in the foyer to pick up concert-goers.
The youngest so far known to have died is eight-year-old Saffie Roussos, while an off-duty Cheshire police officer, who has not yet been named, was also among the dead.
The latest victim to be named is Eilidh MacLeod, a 14-year-old from Barra in the Outer Hebrides, also died. Her family issued a statement saying: "Words cannot express how we feel at losing our darling Eilidh."
Of the 64 injured, 20 are in a critical condition. Twelve of them are children.
Who was the attacker?
Salman Abedi was a 22-year-old born in Manchester to Libyan parents, and a former University of Salford student.
He attended Burnage Academy for Boys in Manchester between 2009 and 2011, and The Manchester College until 2013.
A former classmate told the BBC that Abedi was a "very jokey lad" but also "very short tempered" and would get angry at "the littlest thing".
The man, who did not want to be identified, said Abedi had hung around "the wrong crowd and was very, very gullible".
Before leaving Burnage Academy, Abedi had become "more and more religious", the man added.
A Muslim community worker, who did not want to be identified, has told the BBC that two people who had known Abedi at college had made separate calls five years ago to a hotline to warn about his extremist views.
He said they had been worried that Abedi was "supporting terrorism" and he had expressed the view that "being a suicide bomber was OK".