Universal Music Group, the parent company of Grande's Republic Records label, posted on Facebook: "We are deeply saddened to learn of tonight's (Monday night) devastating event in Manchester".
The victims are being treated at eight hospitals across Greater Manchester, Chief Constable Ian Hopkins said.
There are many children and young people among the dead.
"This is now being treated as a terrorist incident until police know otherwise". More than 200 people were injured, though no one was killed.
Manchester terror attack death toll rises to 22. From the bottom of my heart, I am so so sorry.
One woman tweeted: "The last 3 times I've seen a show at Manchester Arena they didn't check my bag even though I had a backpack on". Police cars, bomb-disposal units and 60 ambulances raced to the scene as the scale of the carnage became clear.
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More than 400 officers were involved in the operation overnight.
"What I also think we need to say people is that the world should not get used to this".
One fan at the concert with his sister described how the explosion happened as fans were leaving the arena.
"A huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the arena", said concertgoer Majid Khan, 22. "We mourn the lives of children and loved ones taken by this cowardly act", the statement continues.
Top political leaders from across the globe have strongly voiced out their condemnation of the deadly suspected terror attack at the Manchester Arena in England, in which nineteen people have been killed and about 50 injured.
Police said Tuesday morning they are still gathering information about the incident and are setting up a telephone hot line to help people locate loved ones.
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Hayley Lunt was staying at a hotel nearby and had taken her 10-year-old daughter Abigail to her first concert at Manchester Arena on Monday evening.
The confusion and fear in the hours afterward was reflected on social media.
Fans who attended the concert have told multiple news outlets that the security at the venue was lax.Many say their bags weren't checked and and security only wanted to know if they were carrying bottles of water. Everybody ran away from that immediate area, ' she said.
Britain's terrorist threat level stands at "severe", the second-highest rung on a five-point scale, meaning an attack is highly likely.
There haven't been any claims of responsibility, but authorities are investigating if it was a suicide attack. They're telling us to wait by the phones.
Armed police officers stand next to a police cordon outside the Manchester Arena, where USA singer Ariana Grande had been performing, in Manchester, northern England, Britain, May 23, 2017.REUTERS/Andrew YatesPolice in Manchester, England, said at least 22 people were confirmed dead following reports of an explosion at an Ariana Grande concert.
Families wait for information after Manchester attack
The bombing could become the deadliest terror incident in the United Kingdom since the 2005 7/7 bombings that killed 52 people. In a statement on the school's Facebook page, the school said Callander was part of the Health and Social Care course.