UPDATE: The attack was later blamed on a homicide bomber who struck in the foyer of the arena, setting off a device packed with nails. ISIS claimed responsibility. Read more, here.

(original story below)

Charles Krauthammer said that even if the explosion at a United Kingdom concert venue was not terror-related, the reaction proved terrorists instilled fear in many Britons.

By mid-evening Eastern, the cause of the explosion at an Ariana Grande concert in Manchester, UK had not been determined.

As FoxNews.com initially reported:

British Transport Police said an explosion occurred in the foyer of Manchester Arena at 10:30 p.m., around the time the concert finished. Others reported hearing two blasts, a discrepancy that could not immediately be reconciled. The cause of the blasts was not immediately confirmed, but bomb disposal units were reportedly at the scene.

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Spokesman Joseph Carozza said Grande, who was performing at the arena as part of her "Dangerous Woman" world tour, was "okay" and added, "we are further investigating what happened."

Witnesses described panic as concertgoers rushed to get out of the arena. Video from inside the arena showed people screaming as they made their way out amid a sea of pink balloons. Some on social media initially suggested that some of the balloons had burst, making a loud noise like a bomb.

Krauthammer noted that Manchester has a history of terror attacks by the Irish Republican Army, but that if the cause was determined to be terror, it would most likely be linked to radical Islam.

Greg Palkot said that the BBC reported the possibility of double-digit fatalities from the explosion.

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