Police announced two new arrests on Thursday in their probe, bringing the total to eight people in custody in Britain.
Earlier on Wednesday, three men were arrested after police executed warrants in South Manchester.
A woman who was arrested in Blackley on Wednesday evening has since been released without charge.
Ariana Grande has officially suspended her global tour behind her album "Dangerous Woman" on Wednesday, following the recent attack on her show in Manchester, England, which left at least 22 dead and 59 others injured.
Salman Abedi, 22, the British-born suicide bomber.
The father and a brother of suspected Manchester suicide bomber Salman Abedi have been detained by security personnel in the Libyan capital, Tripoli, according to witnesses and officials.
Armed police raided the flat on Wednesday but no arrests were made.
In Monday night's attack, 22 people died and almost 60 were sent to hospitals after an explosion struck in the area between the concert venue and the adjacent transit station.
The father has not been charged and was only detained for questioning, Special Deterrent force spokesman Ahmed bin Salem said. Several British newspapers say UK Prime Minister Theresa May will confront US President Donald Trump about the leaks at the North Atlantic Treaty Organisation summit on Thursday.
He said he knew the man from the neighborhood and the mosque but "in the last 15 years, I haven't seen him in trouble at all".
Ariana Grande confirmed she will return to Manchester following the terrorist attack at her concert Monday.
Military personnel have also been deployed to protect Britain's key sites after the national terror-threat level was raised to its highest level from severe to "critical", signifying that another attack may be imminent.
Greater Manchester chief constable Ian Hopkins said: 'It's very clear that this is a network that we are investigating'.
Britain's political parties say they plan to resume campaigning Friday for the June 8 general election Thursday, after putting campaign events on hold to show respect to bombing victims.
He said that, before leaving the school in 2011, Abedi became "more and more religious" and that this might explain why he cut ties with former classmates.
The friends had argued with him, telling him he was wrong but had become so concerned they contacted the police, the community worker said.
France's interior minister said Abedi is believed to have traveled to Syria and had "proven" links with the Islamic State group.