Here are the 10 latest developments in this big story
There were scenes of panic as Grande's audience of largely teen and pre-teen fans fled the 21,000-capacity venue after what was described by witnesses as a "huge bomb-like bang".
Within moments, ambulances and bomb disposal teams were seen rushing to the venue, as city residents opened up their doors to stranded concert-goers after train services were shut down.
The police carried out a controlled explosion in a small park near the venue a few hours after the blast but said the item turned out to be only abandoned clothes.
Train services to and from Manchester Victoria Station -- located under the Arena -- had been cancelled.
"Disruption is expected to continue until the end of the day," National Rail said in a statement.
The incident caused transport chaos, with traffic jams outside the venue.
A witness, Gary Walker, who had gone with his wife to pick up his daughters from the concert, said: "We heard the last song go and then suddenly there was a massive flash and then a bang and smoke." He and his wife were wounded.
Another witness said everyone was screaming and running, dropping their coats and phones, just scrambling to safety.
The Manchester ambulance service warned people to stay away from the site and only to call "for life threatening emergencies" as it had "a large number of resources at the incident".
Greater Manchester Police's chief constable Ian Hopkins said local police in the city were working with national counter-terrorism and intelligence officials on the investigation.