British police say at least 19 people have been killed and 50 wounded in a massive explosion Monday night at a concert arena in Manchester, England.

The explosion occurred just moments after a concert by American pop star Ariana Grande. Authorities say they are treating the blast as a terrorist incident until they know otherwise.

Video from the concert showed thousands of concertgoers scrambling and screaming, trying to escape the building. The incident caused transport chaos, with traffic jams outside the venue and rail services being cancelled.

A number of audience members were seen walking around the building covered in blood. Many in the audience were young girls who are fans of Grande, a singer and actress who has appeared in TV and film roles. A spokesman for her record label said the singer is “okay.”

There are conflicting reports on the number of explosions, with some witnesses saying they heard one while others report hearing two blasts.  

At least one blast took place in a hallway off the concert floor of the 21,000-seat venue, but no one reported seeing smoke or any other typical signs of a terrorist bombing.

Abandoned shoes, phones and jackets were shown on video scattered throughout the arena.

Worried parents who brought their children to the show are crowding the streets outside the building. A nearby hotel has opened its doors to the kids looking for their mothers and fathers.

“It was a huge explosion. You could feel it in your chest. It was chaotic. Everybody was running and screaming just trying to get out,” a concertgoer told Reuters.

Britain’s terrorism alert level is at “severe,” the second highest on the scale. Terrorism officials are meeting in London.

Grande’s “Dangerous Woman Tour” is to support her third studio album, Dangerous Woman. The tour began on February 3 in Phoenix, Arizona. From Manchester, the tour is to move through Europe, including Belgium, Poland, Germany, Switzerland and France,  through the summer with stops in Brazil, Chile, Argentina, Costa Rica, Mexico and on to Japan, Thailand, the Philippines, New Zealand and Australia.
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