- Witness: "It was a really big explosion. Everybody started screaming and running"
- Manchester police: "There are a number of confirmed fatalities and others injured"
British police: 19 dead after blast at Ariana Grande concert in Manchester
(CNN)At least 19 people are dead and about 50 injured in a possible terrorist incident Monday at Manchester Arena in England, where pop singer Ariana Grande was performing, Greater Manchester Police said.
"This is currently being treated as a terrorist incident until police know otherwise," Manchester police said on Twitter.
"We can confirm there was an incident as people were leaving the Ariana Grande show last night. The incident took place outside the venue in a public space. Our thoughts and prayers go out to the victims," police said on Twitter.
Earlier police had warned people to stay away from Manchester Arena after reports of two loud explosions. The crowd was made up of mainly younger people who had come to see Grande in her first of three scheduled concerts in the UK, on her European and Latin American tour.
Ivo Delgado, a witness, told CNN he heard one explosion as the concert was ending. He said there was smoke in a main corridor outside the arena seating and stage area.
"It was a really big explosion. Everybody started screaming and running," he said.
Delgago said: "There were people on the floor ... There was a lot of confusion."
Social media posts from the scene showed panicked concert goers running down the arena's stairs in an attempt to get away.
British Transport Police told CNN it was in the process of closing some transport in the area.
Video from near the scene showed a caravan of ambulances heading to the arena.
Leader of the Labour Party Jeremy Corbyn offered support on Twitter. "Terrible incident in Manchester. My thoughts are with all those affected and our brilliant emergency services."
Musicians such as Ed Sheeran, Nicki Minaj and Katy Perry all offered supportive tweets.
Perry tweeted Monday that she is "Praying for everyone at @ArianaGrande's show."