A further two people who were arrested earlier in the week have been released.
Tributes left in St Ann's Square, Manchester for the people who died in Monday's terror attack at the Manchester Arena.
The singer's fans are mostly children and teenagers and the explosion killed 22 people, ranging from an eight-year-old schoolgirl to parents who had come to pick up their children.
Some reports indicate that the security forces are on the hunt for a second device made by Abedi which may now be with a member of this network.
This undated photo obtained on May 25, 2017 from Facebook shows Manchester-born Salman Abedi, suspect of the recent Manchester terrorist attack. His father, Ramadan, and another brother, 18-year-old Hashim, were detained a day later by Libyan authorities in Tripoli, where they now live.
"I want to reassure people that the arrests that we have made are significant, and initial searches of premises have revealed items that we believe are very important to the investigation", Greater Manchester Police Chief Ian Hopkins said in a Thursday press conference.
"He found a lot of things that is odd", Mohammed El Hadouri, whose pizza shop was searched by police on Friday, told Sky News.
The BBC said that home secretary Amber Rudd was confident the leaks, which she had described as irritating, would now stop.
She posted a link to the Red Cross and Manchester Evening News's fundraising appeal which has raised £5m since the attack.
Manchester police halted their sharing of investigative information with the US through most of Thursday until receiving fresh assurance there would be an end to leaks to the media.
Labour leader Jeremy Corbyn also chided Conservative Prime Minister Theresa May for cutting spending on policing.
The most senior USA diplomat in Britain condemned the leaks as "reprehensible" and said the U.S. government would take action to identify those responsible and stop them.
"This special relationship that exists between our two countries will certainly withstand this particular unfortunate event", he said.
"The alleged leaks coming out of government agencies are deeply troubling".
Meanwhile, national level campaigning for the 8 June general election resumed today after local level campaigns were resumed on Thursday following suspension in the wake of the attacks on Monday night.
"We must be courageous enough to admit that the "war on terror" is simply not working".
"We always need the public's help to defeat terrorism by being extra vigilant and letting us know of any suspicious behaviour or activity". But they were left "furious" by repeated leaks of material shared with their U.S. counterparts, which provided an awkward backdrop for Prime Minister Theresa May's meeting with U.S. President Donald Trump at the North Atlantic Treaty Organisation summit in Brussels later in the day. Based on the account of his younger brother, Hashim, investigators think Abedi used the internet to learn how to make a bomb and "seek victory for the Islamic State", bin Salem said.