Police investigating the Manchester Arena bomb attack have stopped sharing information with the US after leaks to the media.
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 just hours after the attack, which left 22 dead.
Theresa May said she would tell Donald Trump at a Nato meeting that shared intelligence “must remain secure”.
The US’s acting ambassador to the UK “unequivocally condemned” the leaks in a BBC radio interview.
“These leaks were reprehensible, deeply distressing,” Lewis Lukens said.
“We have had communications at the highest level of our government … we are determined to identify these leaks and to stop them.”
Meanwhile, the Queen has been to the Royal Manchester Children’s Hospital visiting some of the injured as well as members of the emergency services.
While there she paid tribute to Manchester and the “extraordinary” way the city had responded to Monday’s attack at an Ariana Grande concert, in which 116 people were also injured.
In total eight men are now in custody following the bombing carried out by Manchester-born Abedi, a 22-year-old from a family of Libyan origin.
The arrests have been “significant” while searches of premises have also yielded items “important to the investigation”, Greater Manchester Police said.
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.
A Whitehall source said Abedi was one of a “pool” of former subjects of interest whose risk remained “subject to review” by the security service and its partners.
In other developments:
A minute’s silence was held at 11:00 BST in remembrance of those who lost their lives or were affected by the attack
Two men were arrested following a search of an address in the Withington area of Greater Manchester on Thursday morning, taking the number of people held to eight
Manchester City and Manchester United have jointly pledged £1m to an emergency fund set up to support the victims
A possible suspicious package was declared safe after army bomb disposal experts were called to a street in Hulme, near Manchester city centre
The Conservatives and Labour are to resume general election campaigning on Friday
Greater Manchester Police hope to resume normal intelligence relationships – a two-way flow of information – soon but is currently “furious”, the BBC understands.
Its chief constable Ian Hopkins said the recent leak had caused “much distress for families that are already suffering terribly with their loss.”.
The force – which is leading the investigation on the ground – gives its information to National Counter-Terrorism, which then shares it across government and – because of the Five Eyes intelligence sharing agreement – with the US, Australia, Canada and New Zealand.
All other US-UK intelligence is still being shared, while five terrorist plots have been disrupted in the UK since the 22 March Westminster attack, the BBC has learned.
Home Secretary Amber Rudd has said she is “confident” the leaks will now end, after having voiced her irritation following the leak of the attacker’s name.
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 an angry response from within Whitehall and from UK police chiefs.
The police decision to stop sharing information specifically about the Manchester attack with their security counterparts in the US is a hugely significant move and shows how angry British authorities are.
The information from the crime scene wasn’t shared on a whim: the British and Americans have a lot of shared world-leading expertise in improvised explosive devices and scientists would be discussing whether the Manchester device tells them something new that could, ultimately, track down a bomb-maker.
Other sharing will continue. The UK and US share a vast amount of information about terror and espionage threats – it is a tight-knit network that also encompasses Canada, Australia and New Zealand.
That system is based on trust and the “control principle”: if a piece of intelligence is shared, the receiving nation has no right to further disseminate it without permission.
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 a delay of about 36 hours before the public know who is being investigated can allow known associates of the suspect to be arrested without being tipped off.
Lord Blair, who was the head of the Metropolitan Police at the time of the bombings in London on 7 July 2005, said a similar leak had happened then.
“It’s a different world in which the US operate in terms of how they publish things and this is a very grievous breach but I’m afraid it’s the same as before,” he said.