The bombing, which took place at the Manchester Arena indoor venue just after the end of a concert by USA pop singer Ariana Grande, was the deadliest in Britain since July 2005, when 52 people were killed in attacks on London's transport network.
Police are trying to determine whether suicide bomber Salman Abedi acted alone when he set off his explosives at the end of a pop concert at a Manchester arena. Azhar Mahmoud, who prays at the mosque in south Manchester, said it was "horrible" that the bomber was associated with it.
Security forces rounded up more suspects Wednesday in the deadly Manchester concert blast and soldiers fanned out across the country to national landmarks as an on-edge Britain tried to thwart the possibility of additional attacks.
The bomb used in the attack appeared to contain carefully packed shrapnel and have a powerful, high velocity charge, according to leaked photographs from the investigation published by the New York Times.
A 12-volt battery was also found at the site, which could be the bomb's power source, the report says.
Police hunting the terror network behind the Manchester Arena bombing have stopped passing information to the United States on the investigation as a major transatlantic row erupted over leaks of key evidence in the USA, according to a report.
Interior minister Amber Rudd had described the leaks as "irritating" early on Thursday, after details about bomber Salman Abedi, including his name, first appeared in USA media, adding that Britain's allies were perfectly clear that it "shouldn't happen again".
"I don't believe that it was him", Ramadan Abedi told the New York Times.
Britain's Home Secretary Amber Rudd says the "element of surprise" in the police and security service measures could be compromised by information being released too quickly.More news: Vettel wins in Monaco to extend his F1 lead
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Britain raced Thursday to track down a jihadist network suspected of orchestrating the Manchester concert attack, as a row escalated between London and Washington over leaked material from the probe.
News concerning the victims of the attack continued to trickle through on Wednesday.
Collomb, who spoke with May after the attack, said the two countries should continue cooperating closely on counterterrorism efforts despite Britain's pending exit from the European Union.
The Islamic State has claimed responsibility for the Manchester bombing, though that claim has not yet been verified by British security officials.
Amber Rudd told Sky News that US officials provided information to the news media that Britain preferred to keep confidential for reasons of operational security.
Separately, a Turkish official told The Associated Press that Abedi travelled through Istanbul and Duesseldorf on his way to Britain.
The British investigation is now reportedly focusing on who helped Abedi, and on whether the bomb-maker is still at large.
Investigators are also still trying to determine whether Abedi received support from family members.
Speaking to reporters on Wednesday, Manchester's police chief stated that it is believed that Salman was part of a "network" and not a so-called "lone-wolf" terrorist.