Unfolding, from BBC News:
Can't help but jump to conclusions, but concerts do have pyrotechnics, heavy equipment, et cetera.Police have confirmed a "number of fatalities" following reports of an explosion at Manchester Arena.
Witnesses reported hearing a "huge bang" following an Ariana Grande gig at Manchester Arena.
....
A number of eyewitnesses have described the confusion in the aftermath.
Robert Tempkin, 22, from Middlesbrough, said: "Everyone was screaming and running, there were coats and people's phones on the floor. People just dropped everything.
"Some people were screaming they'd seen blood but other people were saying it was balloons busting or a speaker had been popped.
"There were lots of ambulances. I saw somebody being treated. I couldn't tell what had happened to him."