The singer is reportedly "devastated that young people who came for a good time are now lying dead and injured" and is "in no condition to perform".
Grande was scheduled to perform on Thursday in London at the O2 Arena.
The explosion was reported “within the foyer area” of the venue about 10:30 p.m., according to the British Transport Police. A tweet from Manchester Arena said the explosion took place “outside the venue in a public space.”
The cause of the explosion was unclear, but Manchester police said on Twitter that “this is currently being treated as a terrorist incident until police know otherwise.”