Nineteen people were killed and 59 others were injured in an explosion about 10:35 p.m. on Monday in the foyer outside the main hall of the Manchester Arena.
■ Prime Minister Theresa May said the police were treating the incident as “an appalling terrorist attack.”
■ The authorities suspect the blast came from either an abandoned backpack or a suicide bomber, a senior American intelligence official said. British officials said they were investigating reports that a suicide bomber detonated an improvised device containing nuts and bolts as shrapnel.
■ The explosion occurred just as a concert by the American pop star Ariana Grande was ending. Traumatized fans, including children, screamed and ran. Ms. Grande was not injured.
■ Britain’s leading parties agreed to suspend campaigning for the June 8 general election out of respect for the victims of the attack.
■ Parents who were separated from their children during the mayhem were told to go to nearby hotels, where many had taken refuge. Other children were being kept in the arena.
‘Everyone Started Crying and Screaming’
Laura Bruce, 18, was with her sister Amy, 25, in one of the arena’s upper tiers when they heard the explosion. “Everyone below us just turned and ran,” she said. “Because we were higher up, we could not get out for five minutes. When we came out, a man walked past us just covered in blood.”
Sophie Tedd, 25, had traveled from Darlington to attend the concert with her friend, Jessica Holmes. At the end of the concert, they heard a loud bang and initially wondered whether “a speaker had blown.”
“Then everyone started crying and screaming,” she said. “Everyone ran out. People were pushing each other out of the way. It took a couple of minutes to get out. The police were outside telling us to keep running, to run away from Victoria station.”
Video from inside the arena showed the surreal scene of people scrambling for the exits amid pink balloons. The balloons were part of choreographed staging for Ms. Grande’s tour, after a segment with projections and lasers.
— Rory Smith and Ben Sisario
The Terrorism Threat in Britain
The Manchester police are working on the assumption that the deadly explosion at the concert was an act of terrorism. If so, it would be the worst act of terrorism in Britain since the 2005 bombings of London’s buses and subway killed 52 people.
But the British authorities, who have foiled numerous terrorist plots, will hardly be surprised. The threat level set by MI5, the domestic intelligence service, has been set at “severe,” the second-highest level, for months, meaning that an attack was considered “highly likely.” And counterterrorism officials have been warning that as the Islamic State comes under more military pressure in Iraq and Syria, it will try to strike abroad.
— Steven Erlanger
Leading Parties Suspend Campaigning
Britain’s leading political parties said they would suspend campaigning for the June 8 general election out of respect for the victims in Monday’s attack.
“I have spoken with the prime minister, and we have agreed that all national campaigning in the general election will be suspended until further notice,” said Jeremy Corbyn, the leader of the opposition Labour Party.
“I am horrified by the horrendous events in Manchester last night,” he added. “My thoughts are with families and friends of those who have died and been injured.”
— Stephen Castle
Desperate Search for Friends and Relatives
Friends and relatives appealed for help locating loved ones who attended the concert.
Charlotte Campbell told CNN that she last spoke to her 15-year-old daughter, Olivia, about 8:30 p.m. “She was enjoying herself, and we’ve not heard anything from her since. We’ve phoned hospitals. We’ve phoned everywhere we can think. We’ve posted on every social network, and there’s nothing,” she said.
She said her daughter was attending the concert as part of a birthday present for a friend who was also missing. “They’re normal teenage children who were going to see their favorite artist, and it’s ended in absolute carnage,” she said.
“It’s the most horrible feeling ever to know your daughter is there and you can’t find her, and you don’t know if she’s dead or alive,” Ms. Campbell said, her voice breaking. “I don’t know how people can do this to innocent children.”
— Philip Pan
Ariana Grande: ‘I Am So So Sorry. I Don’t Have Words.’
Anxious Relatives Gather at Hospital
At one of the hospitals, the Manchester Royal Infirmary, anxious relatives, many in tears, showed up to check on their loved ones. Outside the pediatric emergency department, a van carrying blood supplies pulled in behind an ambulance.
The injured were being treated at six hospitals, said Chief Constable Ian Hopkins of the Greater Manchester Police. The police set up an emergency number — 0161 856 9400 — “for those who are concerned about loved ones or anyone who may have been in the area,” the chief constable said.
— Sewell Chan
Witnesses Describe Possible Nail Bomb
Witnesses said that the explosion appeared to involve the use of a nail bomb. Nail bombs are used to magnify the destructive power of explosives, as the shrapnel increases the bomb’s ability to wound its victims. A nail bomb was believed to have been used Monday in an attack at a military hospital in Bangkok that wounded two dozen people.
Nail bombs use shrapnel like steel balls, razors, screws and other pieces of metal to enhance their destructive capacity. They were used in Britain by the Irish Republican Army in its campaign against the British government, including in a 1981 attack in central London that killed one women and injured 50 others.
— Gerry Mullany
Controlled Explosion Afterward
Speculation that there might be another explosive device rose hours after the blast at the arena when the Manchester police said that they had carried out a “precautionary controlled explosion in Cathedral Garden.” It turned out to have been abandoned clothing, the police said, “not a suspicious item.”
— John Harney
Blast Came After ISIS Plea
Last week, the Islamic State released a 44-minute video featuring fighters of different nationalities, enjoining their supporters back home to carry out acts of violence. Among them was a man identified as a British national, according to a translation of the video provided by the Middle East Media Research Institute, which tracks jihadi propaganda.
Besides the threat last week, ISIS has repeatedly targeted Britain in its propaganda, though with little effect until earlier this year.
— Rukmini Callimachi
Who Is Ariana Grande?
Ms. Grande, 23, began her career as an actress on the children’s television network Nickelodeon. She played the character Cat Valentine — whom she once described as “simple” — on the hit shows “Victorious” and “Sam & Cat.”
“Victorious,” a show about an aspiring teenage singer at a Hollywood high school, ran from 2010 to 2013 and was named favorite TV show at Nickelodeon’s 2012 Kids’ Choice Awards.
“Sam & Cat,” a spinoff of “Victorious,” began in 2013 and chronicled the adventures of two roommates who open an after-school babysitting service. Ms. Grande’s performance won her the favorite TV actress honor at the 2014 Kids’ Choice Awards.
The show was canceled that year after one season. Ms. Grande wrote in a Facebook post at the time that playing Cat Valentine had helped her transition “from teenager to adult.”
“I know a lot of people will think this is a lot for some ‘dumb’ kids’ show character,” she wrote, “but to me she is actually a lot smarter, stronger and braver than all the rest of us.”
A year earlier, Ms. Grande had released “The Way,” a debut single that would propel her nascent music career. The New York Times music critic Jon Caramanica later wrote that she transitioned from teen actress to pop diva through a “combination of exceptional voice, exceptional pluck and an exceptional sense of which hole in the marketplace she could exploit.”
When Monday night’s blast took place outside her concert, Ms. Grande was on a tour to support her 2016 album, “Dangerous Woman.” Reviewing the tour’s February stop at Madison Square Garden, the New York Times music critic Jon Pareles called Ms. Grande’s performance “a show of confidence, prowess and aplomb.”
— Mike Ives
U.S. Intelligence Is Briefed
Intelligence officials in the United States were briefed on the Manchester explosion late Monday and were told it appeared to be a terrorist attack, said one senior official who was not authorized to discuss the situation publicly and spoke on the condition of anonymity.
The authorities believed the blast came either from an abandoned backpack at the arena or a suicide bomber, said a senior United States intelligence official who was briefed on the attack.
British intelligence and counterterrorism officials said late Monday that they were “treating the incident as terrorism,” while investigating reports of a possible suicide bomber detonating an improvised explosive containing shrapnel.
The Department of Homeland Security said that it was monitoring the situation and that it had “no information to indicate a specific credible threat involving music venues in the United States,” while warning Americans in Manchester to be vigilant.
— Adam Goldman and Eric Schmitt
Reaction From Other Music Stars
Arena Largest Such Venue in Britain
The Manchester Arena is the largest indoor venue in Britain, with a capacity of 21,000, or 18,000 for concerts. It was constructed as part of Manchester’s bid to host the Olympic Games in 1996 and 2000, and is connected to the Manchester Victoria Station, which was closed because of the attack.
The arena opened in 1995 and has hosted some of the world’s leading musical acts, including The Rolling Stones, U2, Madonna and Luciano Pavarotti. It also hosted the 2002 Commonwealth Games.
— Gerry Mullany
Rail Service at Busy Hub to Remain Suspended
Rail service at Manchester Victoria, a major transportation hub in the city, was suspended late Monday night and will remain closed on Tuesday. Manchester’s light rail service, Metrolink, has also been suspended at the station.
Manchester Victoria, which was used by more than 7 million passengers in 2015-16, is one of the busiest rail stations in England.
— Matthew Haag
Company Describes Security at Arena
The Pennsylvania-based company SMG manages the Manchester Arena, and Wes Westley, the president and CEO of the company, described the precautions at the venue.
“It is obviously as tight security as anywhere in the states,” he said in an interview. “Backpacks are not allowed. Drinks are taken away from people. You have to go through very strict security to enter the arena.”
He explained that attendees arrive through a large public foyer, which is where the explosion occurred. The area, which connects to the Manchester Victoria rail station, is where parents often wait for their children after concerts.
The incident “occurred in a public space outside of Manchester Arena,” the company said.
— Ben Sisario