Local police said 19 people have died and about 50 were injured at Manchester Arena as one or two explosions rocked the venue in England during an Ariana Grande concert on the evening of Monday, May 22. Authorities said it would be treated as a terror incident “until police know otherwise,” according to a Greater Manchester Police statement.

Other reports, including one from NBC News, stated that as many as 20 people had perished. It wasn't clear if people were affected by the explosion or by a possible stampede as fans in the 21,000-capacity arena evacuated.

The explosion or explosions were heard about 10:45 p.m. local time, according BBC World News. Grande, who's based in Los Angeles, was said to be OK. Witnesses said she was at the end of her set when they heard a loud bang.

“The whole building shook,” one witness told BBC. The network said the source of the sound was a box office or foyer that's not a part of the main arena.

Video of the evacuation captured pandemonium and panic.

We will have more on this story as it develops.

[Editor's note: This story was updated with fatality and injury figures from police at 5:20 p.m.]

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