UPDATE 7:22pm PST | The US Department of Homeland Security has issued a statement saying it is “closely monitoring the situation at Manchester Arena” and that there could be “increased security” in public places and music events in the US:
We are working with our foreign counterparts to obtain additional information about the cause of the reported explosion as well as the extent of injuries and fatalities.
US citizens in the area should heed direction from local authorities and maintain security awareness. We encourage any affected US citizens who need assistance to contact the US embassy in London and follow department of state guidance. 
At this time, we have no information to indicate a specific credible threat involving music venues in the United States. However, the public may experience increased security in and around public places and events as officials take additional precautions.
We stand ready to assist our friends and allies in the UK in all ways necessary as they investigate and recover from this incident.
Our thoughts and prayers are with those affected by this incident.
UPDATE 5:32pm PST | Manchester Arena confirms the original explosion occurred outside the venue in a public space.
— AO Arena (@AOArena) May 23, 2017
Manchester Police found a second device and will execute a controlled explosion.
There will be a controlled explosion in Cathedral gardens shortly if you hearing anything don't be concerned.
— Greater Manchester Police (@gmpolice) May 23, 2017
UPDATE 5:14pm PST | Manchester police confirm 19 dead, and around 50 others injured. It is being treated as a terrorist incident until learned otherwise.
Latest statement on incident at Manchester Arena pic.twitter.com/BEpLOan3dY
— Greater Manchester Police (@gmpolice) May 23, 2017
Just after Ariana Grande wrapped up a concert tonight in Manchester, England, a bomb-like noise reportedly went off and caused a massive panic within the stadium. The explosion came from the area near the box office where merchandise was being sold. Authorities are still unsure of the cause of the explosion; though casualties have already been reported, the exact number has not been released.
https://twitter.com/hannawwh/status/866775833553379328
“We were all exiting the venue when around 10:40 to 10:45 p.m.-ish a huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the area,” a concertgoer told the Guardian.
The arena where the concert was held has a capacity of up to 21,000. Those living around the venue report scenes of thousands of people rushing out in a panic.
A bomb disposal unit was called on-site. It is not clear if further bombs or incendiary devices were found as this is standard protocol in such situations. A representative for Ariana Grande said the singer is okay, and they are investigating what happened.
Police are warning people to stay away from the area.
For live updates on the scene, visit the Guardian.
Police statement on incident at Manchester Arena pic.twitter.com/gaKASukx9a
— Greater Manchester Police (@gmpolice) May 22, 2017
Details of a casualty bureau for incident at Manchester Arena will be shared as soon as available. Please stay away from the area
— Greater Manchester Police (@gmpolice) May 22, 2017
Below are some videos taken during the panic. Warning: some of the content might be graphic to viewers.
BREAKING NEWS MANCHESTER EXPLOSION
– At arena
– During Ariana Grande show
– At least 20 dead
– At least 100 injuredpic.twitter.com/3eYPiYinqK— NOTICIERO ANIMAL ® 🐾 (@NoticieroAnimal) May 22, 2017
Video shows chaotic scene outside Manchester Arena amid reports of explosion, deaths after Ariana Grande concert. https://t.co/zEacQKaVwV pic.twitter.com/XoTQ1ufEeC
— ABC News (@ABC) May 22, 2017
Alleged video of the explosion at the @ArianaGrande concert in Manchester. Praying everyone is okay ❤️ https://t.co/Cw7Q3P5qhj
— 🖤 i’m the drama 🖤 OUT NOW (@GreatSongsOnly) May 22, 2017
Eye-witness: "thrown 30 feet" following "explosion" at Ariana Grande concert https://t.co/WhXoeUBbSu via @youtube
— Mark Frankel (@markfrankel29) May 22, 2017
https://twitter.com/johnnyghicas/status/866835006643216384
