A suicide bomber killed at least 22 people and injured 59 others by detonating an explosive at the Manchester Arena in England during an an Ariana Grande concert Monday night, the Greater Manchester Police say.

The attacker, identified by CBS News as Salman Abedi, died at the scene and is believed to have used an improvised explosive device, police said.

ISIS has claimed responsibility for the attack.

Witnesses said a loud explosion was followed by screams, panic and a stamped of people trying to leave the crowded building, which is one of the largest indoor arenas in the world.

NBC NEWS SPECIAL REPORT https://t.co/N2lOT9C8KS — NBC Nightly News (@NBCNightlyNews) May 22, 2017

Ariana Grande was not among those injured, her representatives said. The incident reported about 10:30 p.m. local time, after Grande left the stage and houselights came on, while people were beginning to exit the arena. About 20,000 people were in attendance at the sold-out show, including many teenagers and young people who came to see the pop star perform. The blast occurred in a public area just outside the arena and the “security perimeter.”

Grande tweeted, “broken. from the bottom of my heart, i am so so sorry. i don’t have words.”

broken.

from the bottom of my heart, i am so so sorry. i don't have words. — Ariana Grande (@ArianaGrande) May 23, 2017

North West Ambulance, the local medical service, said it has taken 59 casualties from the Manchester Arena to various local hospitals, and has also treated a number of “walking wounded” at the scene.

Children, including young girls, are among the victims. The first victim of the attack has been identified as 18-year-old Georgina Callandar.

The Greater Manchester Police said on Twitter, “An emergency number is available for those who are concerned about loved ones or anyone who may have been in the area – 0161 856 9400.”

The North West Counter Terrorism Unit is treating the incident as a possible terrorist incident and is investigating, the BBC reports.

The investigation is ongoing, Greater Manchester Police said.

“We are currently treating this as a terrorist incident until we know otherwise. We are working closely with the national counter terrorism policing network and UK intelligence partners,” Chief Constable Ian Hopkins said in a statement. “This is clearly a concerning time for people but we are doing all we can working with local and national agencies to support those affected and gather information about what has happened tonight. As you will understand we are still receiving information and updates so will provide more details when we have a clearer picture.”

Hopkins added,” I want to thank people for their support and would ask them to remain vigilant and if they have any concerns report them in confidence to us on the Anti-Terrorist Hotline 0800 789321. It is important people avoid the area so that we can effectively deal with the incident.”

You can watch a live stream of news coverage here.

This story is still developing. Here is what we know so far:

1. The Explosion Occurred Near the Foyer Area of the Arena & CCTV Camera Caught the Bomber Arriving on the Tube Before Blowing Himself Up

The explosion occurred near the foyer area of the arena, British Transport Police told The Sun. Sources told the newspaper the explosion was a “nail bomb attack,” but police have not confirmed that detail.

NHS sources are saying the explosion at Manchester Arena was a nail bomb attack. Still unconfirmed. — Tom Newton Dunn (@tnewtondunn) May 22, 2017

NBC News is reporting that it was an attack carried out by a suicide bomber wearing a backpack bomb. NBC News’ Pete Williams, citing U.S. sources, reports there is “increasing confidence” it was a terror attack, while forensic evidence points to a bomb in a backpack.

NBC News: UK authorities suspect a possible suicide bomber responsible for incident at Ariana Grande concert in Manchester sources say. — Tom Winter (@Tom_Winter) May 23, 2017

CBS News is reporting a bomber blew himself up at the arena. According to the CBS report, the bomber took the Tube to Victoria Station, went to the ticket area of the arena and detonated an explosive device as people left the concert. Investigators found ball bearings at the scene and have traced the bomber’s movements through CCTV cameras.

Lauren Valentine Barrow, a local singer and concert booking agent, posted on Facebook, “I have heard from quite a few people that know staff from the arena saying that there were suicide bombers at the foyer entrance near McDonald’s. It’s not confirmed of course but all the things I am hearing are not good. I hope you are all safe.”

Police have released few details about the incident, including what led to the deaths and injuries. Early reporters indicated equipment exploded, sparking a panic. There were also reports early on of multiple explosions, but many witnesses have since described hearing only one blast. Concertgoers were holding pink balloons handed out by Ariana Grande’s team as part of the concert, and popping balloons were possibly mistaken for gunshots.

Wtf is happening in Manchester arena? Massive bang & everyone is running & screaming, people are crying — Rebecca B (@RebeccaBx) May 22, 2017

“There were just a loud bang and a flash and everyone tried to scramble out. An alarm came on telling everyone to stay calm but leave as quickly as possible,” Jade Baynes, 18, of Hull, told The Guardian. Another witness, Oliver Jones, also gave a description to The Guardian of what he witnessed:

I was in the toilet and heard a loud bang just after the concert had finished and people had started to leave. The bang echoed around the foyer of the arena and people started to run. I seen people running and screaming towards one direction and then many were turning around to run back the other way. Security was running out as well as the fans and concert goers. Reports of blood and people injured. In so much shock and panic. You see this on the news all the time and never expect it to happen to you. I just had to run and make sure me and my sister were safe.

Another witness told the BBC she saw some people being injured in the stampede as people tried to exit after the blast.

“As we turned around the corner there was an horrific stampede of people coming down the steps, people falling on floor,” she told the news station. “I grabbed my daughter and we just ran. There were people being crushed on the floor.”

The chaos outside #manchesterarena when we were all trying to get out?I hope everyone is okay ❤️ #Manchester pic.twitter.com/ISgx3AzJTF — jordan mcbrearty (@JSMcbrearty) May 22, 2017

A video posted to Twitter, which you can watch below, shows armed police pulling a man out of a car and arresting him. The person who posted the video did not know the circumstances surrounding the arrest, which occurred in Manchester near the arena. Police have said they are looking into whether the bomber was connected to a network or was working alone. It is not clear if the man seen in the video was later released or remains in custody.

Armed polices just pulled a man out of a car and arrested him pic.twitter.com/nQF37PfjHF — Tas (@DrNinja_) May 22, 2017

The U.K. terror alert was at “severe” before the explosion. The incident comes after an attacker inspired by the ISIS terror group drove a car into pedestrians on the Westminster Bridge in London, killing four people and injuring more than 50, before crashing his car into the fence of the British Parliament and fatally stabbing a police officer. The terrorist, Khalid Masood, was then shot dead by another officer.

The incident also comes after raids on terror groups in London that led to at least four arrests, The Guardian reported on May 17. Police said the four men were arrested on “suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.” Met Police said, ” These arrests were pre-planned as part of an ongoing investigation by the Met’s counter-terrorism command and MI5. The arrests are linked to activity in the UK.” Police also carried out raids in late April, leading to arrests that they say disrupted two separate attack plots, including one man arrested in Westminster and another in north west London, where a woman was shot and subsequently charged criminally along with two other women.

The explosion also comes on the fourth anniversary of the death of a British Army soldier, Fusilier Lee Rigby, who was publicly executed by Islamic terrorists.

ISIS supporters immediately began celebrating the attack on social media, and the group officially claimed responsibility on Tuesday through its Amaq News Agency, according to the SITE Intelligence Group.

“With Allah’s grace and support, a soldier of Khilafah managed to place explosive devices in the midst of the gatherings of the Crusaders in the British city of Manchester, in revenge for Allah’s religion, in an endeavor to terrorize the mushirkin and in response to their transgressions against the lands of the Muslims,” the statement said. “The explosive devices were detonated in the shameless concert arena, resulting in 30 Crusaders being killed and 70 others being wounded. And what comes next will be more severe on the worshipers of the Cross and their allies, by Allah’s permission. And all praises is due to Allah, Lord of the creation.”

The statement called him a soldier of the Khilafah, or caliphate. It also says the attack was meant to terrorize the “mushirkin,” which means pagans or those who worship a false idol.

According to CBS News, experts are somewhat skeptical of ISIS’ claim of responsibility, saying the details of the statement do not match up with the actual events. The ISIS statement says multiple devices were detonated, while officials say there was only one explosion, among other inconsistencies, including the number of victims. ISIS has at times claimed an attack when it had no direct role in the planning and execution of it, but did influence a supporter to kill on its behalf.

Rukmini Callimachi, New York Times reporter who covers ISIS and is a leading expert on the group, tweeted, “So far officials indicated that the attack was likely carried out by a single suicide bomber. Claim suggests it was devices left behind … The chain of custody of this claim and its release on Telegram via Nashir, it’s timing and language is all in keeping with past claims. … What’s not divulged is whether ISIS had contact with the attacker. Remember ISIS considers inspired attacks to be part of core strategy.”

U.S. President Donald Trump, who is traveling in Israel, has been briefed, a senior White House official told NBC News. The NYPD, FBI and other law enforcement have said they are taking precautions in the United States as a result of the Manchester incident. But the Department of Homeland Security said Monday night there is no specific credible threat to U.S. arenas or concert venues.

National Security Team is providing updates to @POTUS on situation in #manchesterexplosion — Sean Spicer (@PressSec) May 23, 2017

“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,” the U.S. Department of Homeland Security said in a statement Monday night. “U.S. citizens in the area should heed direction from local authorities and maintain security awareness. We encourage any affected U.S. citizens who need assistance to contact the U.S. Embassy in London and follow Department of State guidance.”

DHS also said it is ready to help its counterparts in the U.K. in their investigation.

2. Videos Show the Moment a Loud Blast Was Witnessed Outside the Arena & Captured Chaos Inside

If you look towards the left you see the explosion and hear the bang. I hope to GOD everyone is ok, and so glad Jess and Em are. #manchester pic.twitter.com/q81KHGEJ6E — Joe Gregory (@JoeAaronGregory) May 22, 2017

A video posted to Twitter claims to show the moment the explosion occurred. The footage was recorded by a dashboard camera. After a few seconds a bright light can be seen near the building and a loud blast can be heard.

A second video showed people inside the arena as the blast was heard:

Another video showed the chaos outside:

Two loud bangs heard around Manchester arena. People running out of the arena. No idea what's going on pic.twitter.com/KaRzQckvEE — Alan Brennan (@alanbmufc92) May 22, 2017

A witness, Ivo Delgado, told CNN the incident occurred after the concert was ended and while people were beginning to leave. Delgado told the news network he heard a loud bang and saw a little bit of smoke, along with people on the floor who were injured. He said a lot of people were screaming, including many “little girls.”

EXPLOSION AT MANCHESTER ARENA AND EVERYONE RAN OUT SO SCARY? pic.twitter.com/pJbUBoELtE — ♡♡ (@hannawwh) May 22, 2017

Videos showed panic inside and outside of the Manchester Arena after the explosion. People went running, witnesses said.

Panicking at Victoria Station after @ArianaGrande concert. Hope everyone is all safe and well. pic.twitter.com/6Q5WNXFkFO — Zach Bruce (@Zach_bruce) May 22, 2017

People also spilled into Victoria Station, which is located at the arena.

Police have asked anyone with images or footage from the incident to upload them to ukpoliceimageappeal.co.uk or ukpoliceimageappealo.com.

You can watch other videos at the link below:

3. Police & Ambulances Flooded the Area Around the Arena, Which Remains Closed Down

well… ariana grande concert manchester pic.twitter.com/It2vnPsWPz — c h a r ? (@charlottefa1ry) May 22, 2017

A large police presence could be seen outside the arena. The area remains closed down and police have asked people to stay away while the incident is investigated.

“Please AVOID the area as first responders work tirelessly at the scene,” Greater Manchester Police said.

People are still emerging, shell shocked: a family from Pontefract say they saw a woman stagger out, on open wound exposed all down one leg — Helen Pidd (@helenpidd) May 22, 2017

Wounded people could be seen leaving the arena, according to reporters.

“We’ve had a few people in with panic attacks and in all kinds of disarray. We’ve got four girls here – trying to get them sorted to get picked up. There was a gentleman on the floor with his leg all bleeding and woman with blood down one side of her face,” tyler, a bartender at the Steven Charles Snooker Club, told The Guardian. “We felt something but didn’t know what it was – there was a sound like thunder. One girl had a panic attack and another had streaming tears, a woman had a heart attack just outside.”

Armed police and helicopters overhead in Manchester, around the corner from the arena. All roads into town blocked off. pic.twitter.com/KMxniNNC3c — Frances Perraudin (@fperraudin) May 22, 2017

Ambulances were streaming to the scene and helicopters could be seen above.

Bomb disposal going into the arena. pic.twitter.com/FG3g4CkpoM — Frances Perraudin (@fperraudin) May 22, 2017

A bomb disposal unit could be seen going into the arena. And a controlled explosion was carried out several hours after the incident because of a suspicious package:

The controlled explosion on BBC News pic.twitter.com/or3fQd5ODJ — ~ (@afterglowlovato) May 23, 2017

The local ambulance service told The Guardian people should only call for “life-threatening emergencies,” adding that there has been a “large number of resources” directed to the incident already.

Greater Manchester Chief Constable Ian Hopkins told reporters, “This has been the most horrific incident we have had to face in Greater Manchester and one that we all hoped we would never see.”

Hopkins said more than 400 officers have been involved in the operation through the night into Tuesday morning.

“This is a fast-moving investigation and we have significant resources deployed to both the investigation and the visible patrols that people will see across Greater Manchester as they wake up to news of the events last night. This will include armed officers as people would expect,” Hopkins said.

London Metropolitan Police said they are standing by Manchester and also planned to increase the police presence in the city on Tuesday.

Police have released few details about the bomber.

“We would ask people not to speculate on his details or to share names,” Hopkins said. “There is a complex and wide ranging investigation underway. Our priority is to work with the National Counter Terrorist Policing Network and UK intelligence services to establish more details about the individual who carried out this attack.”

Hopkins would not say if the man believed to be the bomber was known to police prior to the incident.

“We have received tremendous support from across the police services and partner agencies throughout the night,” Hopkins said. “We regularly carry out exercises to test our ability ro respond to such incidents and this has ensured a very swift response from local and national agencies.”

Hopkins said a large cordon remains in place around Manchester Arena and the Victoria Train Station, which will be in place for some time.

“Terrorists attempt to disrupt our lives and create distrust and fear in communities,” Hopkins said. “We have a long history in Greater Manchester of communities standing together during difficult times. In the coming days we will be working closely with community leaders to address any issues. It is important that we all continue to remain vigilant, but also to go about our daily lives.”

Hopkins added, “As people are waking up to this tragic news on what is a sad day for Greater Manchester, the officers and staff from Greater Manchester Police and the other emergency services will continue to do all they can to help get us through the difficult days ahead.”

4. The Arena is Located Near the Center of Manchester & Has a Capacity of 21,000 People

The arena is located in Hunts Bank, Manchester, immediately north of the center of the city, according to its website. The building was opened in 1995 and is one of the busiest indoor arenas in the world, hosting concerts and sporting events, including boxing and swimming.

It is managed by SMG Europe. The arena’s management has not yet released a statement about the incident. In a statement, Manchester Arena said, “We can confirm there was an incident as peopel 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.”

“Since opening in 1995, the Arena has hosted the biggest names in live entertainment including U2, The Rolling Stones, Madonna, Lady Gaga, Pavarotti and the record-breaking 2010/2011 residency by local comedian Peter Kay,” the arena’s website says. “Manchester Arena has also played a key part in the city’s rich musical heritage with historic shows by local bands Take That, Oasis, Elbow, New Order, James, Happy Mondays, The Charlatans, Noel Gallagher’s High Flying Birds, M People, Doves, Inspiral Carpets, The Verve, Simply Red and The Courteeners. Attracting over one million visitors each year, the 21,000 capacity Arena is a former winner of the industry’s prestigious International Venue of the Year award.”

Manchester is located in the North West area of England. It is home to about 500,000 people, and is part of the second-largest urban area in the United Kingdom, with 2.55 million people living in the Greater Manchester area.

Pat Carney, a council spokesman for the Manchester city center, told the BBC, “It’s a very easy target – a concert hall where young people are enjoying music. The public are really co-operating by staying away from what is basically now a crime site. The world we live in, police and the council have emergency procedures that we practise all the time. Obviously everyone in the city is shocked, having seen how young some of these people are. The police are treating it as a live site, we don’t know if this is the end or there are other incidents in that area… we don’t know at the moment.”

5. Ariana Grande, Her Band & Other Performers Were Not Injured in the Incident, a Spokesman Says

GUYS WE ARE OKAY !!! THANK YOU WE LOVE YOU ??❤️ — B I A ⚡️ (@PericoPrincess) May 22, 2017

Ariana Grande and her band were not injured in the incident, according to a statement from her representative.

“Ariana is okay,” a representative told Billboard. They said the are looking into what happened and have not commented further.

BIA, the supporting act for the concert, tweeted that she and her team are also “okay.”

Grande, 23, is on an international tour for her latest album, “Dangerous Woman,” and is set to perform shows in London on May 25 and 26. But TMZ reports her tour has been suspended indefinitely. TMZ reports Grande is “inconsolable” and “in hysterics” after the bombing.

“”We mourn the lives of children and loved ones taken by this cowardly act,” her manager, Scooter Braun, said in a statement. “We ask all of you to hold the victims, their families, and all those affected in your hearts and prayers.”

Details about the victims have not yet been released.

The U.S. Embassy in London issued a statement about the incident:

The U.S. Embassy in London informs U.S. citizens that there has been an incident at Manchester Arena. Emergency services are currently responding to reports of an explosion at the arena. U.S. citizens should heed guidance from local authorities and maintain security awareness. View updates from the Greater Manchester Police on Facebook @GtrManchesterPolice or on Twitter @GMPolice. Please monitor media and local information sources and factor updated information into personal travel plans and activities. We strongly encourage U.S. citizens in the United Kingdom to directly contact concerned family members in the United States to advise them of your safety.

You can find more information from the Embassy here.