British police arrested a 23-year-old man, raided a property in southern Manchester and carried out a controlled explosion in another part of the city on Tuesday in a fast-moving investigation into a suicide bombing at a pop concert.
Twenty-two people were killed, including children, and dozens wounded in the attack claimed by Islamic State. The blast came just after U.S. singer Ariana Grande finished her concert for an audience mainly of young girls in central Manchester on Monday night.
Greater Manchester Police gave no further details about the arrest but said they had executed warrants in the districts of Whalley Range and Fallowfield, three miles south of the city centre, where a controlled explosion took place.
The attack led to a large-scale investigation by the Manchester police, who asked for drivers with dashboard cameras to hand them any film they took late on Monday.
Police sealed off an entrance to dozens of terraced houses in Fallowfield, where a witness said armed police surrounded a property.
"Police ... gained entry to the property using an explosive charge to take the door off," said Neville Edwards, an events safety adviser, 32, whose mother's house backs onto the property which was raided.
"Within moments of that there were reports of a gentleman being whisked off."
In Whalley Range in southern Manchester, witnesses said armed police had surrounded a newly-built apartment block on a usually quiet tree-lined street.
Mussab Amari said he saw lots of police cars and vans. "They just came in and surrounded everywhere. Everyone was armed."
A resident of the block said: "A variety of people live here. Arabs, English, Kurds, from lots of different nationalities."
"I think all of them have families," said the man, who declined to be named, standing outside with his partner and son.
Asghar Ali, 51, who lives opposite the building the police had cordoned off, described the street as quiet and "a good area".