Two men have been arrested by counter-terror police in Greater Manchester in connection with Monday's attack, bringing the number in UK custody to eight.
One of the men was detained following searches of an address in the Withington area of the city, while another was arrested in a part of Greater Manchester that was not disclosed.
A woman arrested in the Blackley area of Manchester on Wednesday has been released without charge.
The eight men are in custody following raids across Manchester, Wigan and Nuneaton, and Warwickshire, following the attack by suicide bomber Salman Abedi that claimed 22 lives.
Police carried out a controlled explosion at a property in the Moss Side area of Manchester, although no arrests were reported.
Abedi's father, Ramadan Abedi, was arrested in Tripoli with his brother Hashim, who Libyan security forces said was "aware of all the details" of the attack.
A 23-year-old man - named in reports as Abedi's older brother Ismail - was detained in Chorlton, south Manchester, on Tuesday.
Ramadan Abedi had earlier claimed his son Salman was innocent, saying: "We don't believe in killing innocents. This is not us."
