Britain on Saturday reduced its terror threat level from critical - its highest level - to severe.
A police officer guards the entrance to a street in the Moss Side area of Manchester during an operation as part of the investigation into the suicide bombing on Monday 22.
Of the arrests, two have been released without charges and 12 men remain in custody for questioning.
"The operation is still really at full-tilt in a way and so until the operation is complete we can´t be entirely sure that it´s closed".
Earlier on Sunday, Home Secretary Amber Rudd said investigators can not be entirely sure that Salman Abedi's terror network has been dismantled - and warned other members of the bomber's group are "potentially" still at large.
Leaked info 'undermines' Manchester attack probe
The statement went on to say the damage is greater when information is leaked in the middle of a major investigation. The parents of 14-year Eilidh MacLeod, from the Hebridean island of Barra, confirmed on Thursday that she also died.
According to Greater Manchester Police, the 22-year-old, Briton born to Libyan parents, probably assembled his bomb in an apartment in the city center. "So we're continuing to build on better relationships with the internet, to ask them as the experts to make those changes so that people don't get radicalized and the terrorists don't have somewhere to hide".
On Friday, UK Security Minister Ben Wallace told CNN in Manchester that there are "over 400 investigations now ongoing by the security services and police into terrorist planning or people thinking about terrorist planning".
Police said they are working "around-the-clock" with more than 1,000 people involved in the investigation, pursuing more than 1,500 "actions".
Abedi had been a former "subject of interest" to MI5, but Ms Rudd said: "The intelligence services are still collecting information about him and about the people around him".
Greater Manchester Police made an appeal to the public for information about the bomber's movements since 18 May, when he returned to the UK.
Abedi's city centre flat was one of the last places he went - and where he may have made the final touches to his explosive device - before going to the arena, police have said.
The singer said she will think of the victims "with everything I do for the rest of my life", adding: "They will be on my mind and in my heart everyday".