Police have confirmed they are investigating a 'network' in connection with the Manchester bombing as it emerged an off-duty female officer was killed in the atrocity.
As a huge inquiry into the attack continued, the father of perpetrator Salman Abedi claimed his son was innocent, saying: "We don't believe in killing innocents. This is not us."
In other developments today, detectives made a further three arrests in connection with the investigation, taking the number of people in custody to four.
Twenty-two people were killed and dozens more seriously injured when Abedi, 22, detonated a device as fans left Manchester Arena, where US star Ariana Grande was performing on Monday night.
Greater Manchester Police Chief Constable Ian Hopkins said the level of activity in the probe is "intense" and continuing "at pace".
Asked if officers are looking for the person who made the bomb, he said: "I think it's very clear that this is a network that we are investigating and as I've said, it continues at pace, this extensive investigation is going on and activity taking place across Greater Manchester as we speak."
Mr Hopkins confirmed that one of the victims of the attack was a serving police officer but provided no further details.
Vigils for the attack continue tonight, with Rotherham residents paying their respects at the Heart of Steel Monument in the Minster Gardens from 6.30pm.
The Sheffield vigil took place at the Peace Gardens last night.