The Islamic State group claimed responsibility for the Monday night carnage, which counted children as young as 8 among its victims and left 59 people wounded. British police raided two sites in the northern English city and arrested a 23-year-old man at a third location.
British Prime Minister Theresa May and police said the bomber died in the attack on Manchester Arena - a detail that was not included in the Islamic State claim, which also had discrepancies with the events described by British officials. A top U.S. intelligence official, Dan Coats, said the claim had not been verified by the U.S. government.
PHOTOS: Explosion reported at Ariana Grande concert in UK
Manchester police chief Ian Hopkins identified the bombing suspect as 22-year-old Salman Abedi but gave no other details. A European security official, speaking on condition of anonymity because he was not authorized to speak about the ongoing investigation, said Abedi was a Briton of Libyan descent. British election rolls listed him as living at a modest red brick semi-detached house in a mixed suburb of Manchester where police performed a controlled explosion Tuesday afternoon.
Natalie Daley, who lived in a nearby home, said she was frightened by a loud bang Tuesday, then police yelling, "Get in your houses - get away from the windows!"
"When it's like two seconds from your house, when you walk past it every day, you do live in fear," Daley said.
Manchester, 160 miles (260 kilometers) northwest of London, is one of Britain's largest cities and Manchester Arena is one of the world's largest indoor concert venues.
WATCH: Mother recounts chaotic scene outside Manchester Arena
Campaigning for Britain's June 8 national election was suspended in the aftermath of the attack, the deadliest in Britain since four suicide bombers killed 52 London commuters on subway trains and a bus in July 2005.
In attacking the concert, the bomber targeted an audience full of teenagers and 'tweens - Grande fans who call themselves "Arianators." Teenage screams filled the arena just after the explosion Monday night as fans, many clutching pink plastic balloons, scrambled in panic for exits at the 21,000-capacity arena, tumbling over guardrails and each other to escape.
The attack sparked a nightlong search for loved-ones - parents for the children they had accompanied or had been waiting to pick up, and friends for each other after groups were scattered by the blast. Twitter and Facebook lit up with heartbreaking appeals for the missing.
"I've called the hospitals. I've called all the places, the hotels where people said that children have been taken and I've called the police," Charlotte Campbell tearfully told ITV television's Good Morning Britain breakfast show. Campbell's 15-year-old daughter, Olivia, had attended the show with a friend who was wounded and being treated in a hospital.
"She's not turned up," Campbell said of her daughter. "We can't get through to her."
An 8-year-old girl was among the dead - the youngest known victim - and her mother and sister were among the wounded in what May called "a callous terrorist attack." The wounded included 12 children under age 16, hospital officials said.
"We struggle to comprehend the warped and twisted mind that sees a room packed with young children not as a scene to cherish but as an opportunity for carnage," May said.
Some concert-goers said security was haphazard before the show, with some people being searched and others allowed inside unhindered. The bombing took place at the end of the concert, when the audience was streaming toward the city's main train station.
Witnesses said the blast scattered bolts and other bits of metal, apparently intended to maximize injuries and deaths.
"It was carnage. Everyone was scrambling over each other. ... It was just a race to get out really," said 14-year-old Charlotte Fairclough, who got tickets as a Christmas present.
Outside the arena, bleeding victims lay on the pavement. "As we came outside to Victoria Station, there were just people all over the floor covered in blood," said 25-year-old Ryan Molloy. "My partner was helping to try to stem the blood from this one person. ... They were pouring blood from their leg. It was just awful."
The train station, which is adjacent to the arena, was shut down for coming days, authorities said.
With public transport halted, Manchester residents opened their hearts. Taxis offered stranded people free rides home while some residents invited those without lodging into their homes. Twitter users circulated the MissinginManchester hashtag to help people looking for family and friends.
Grande, who was not injured in the blast, tweeted: "broken. from the bottom of my heart, i am so so sorry. i don't have words."
Hayley Lunt had taken her 10-year-old daughter Abigail to her first concert. She said the explosions rang out as soon as Grande left the stage.
"We just ran as fast as we could to get away," Lunt said. "What should have been a superb evening is now just horrible."
Britain's Queen Elizabeth II marked a moment of silence Tuesday afternoon to honor the victims. Accompanied by her husband Prince Philip, as well as Prince Charles and his wife Camilla, the queen stood at the top of the steps leading down from Buckingham Palace as the national anthem played.
The first confirmed victim was Georgina Callander, whose death was reported by her former school. The Bishop Rawstorne Church of England Academy in Croston, northwest of Manchester, posted a photo of Georgina on its website, smiling in her school uniform. It described her as "a lovely young student who was very popular with her peers and the staff."
Eight-year-old Saffie Roussos, the youngest victim identified, was described as "simply a beautiful little girl in every aspect of the word. She was loved by everyone and her warmth and kindness will be remembered fondly," said the head teacher of the Tarleton Community Primary School in Lancashire.
The Islamic State group's claim of responsibility echoed others the extremists have made for attacks in the West but with vague details that left open the possibility it was an opportunistic attempt at propaganda.
U.S. President Donald Trump, visiting the West Bank city of Bethlehem, said the attack preyed upon children and described those responsible as "evil losers."
"This wicked ideology must be obliterated. And I mean completely obliterated," he said.
After Manchester, Grande was due to perform in London on Thursday and Friday, and later at venues elsewhere in Europe, including Belgium, Poland, Germany, Switzerland and France, with concerts in Latin America and Asia to follow.
Grande's tour has not been canceled or postponed despite reports online, said a person close to the situation, speaking on condition of anonymity because they were not allowed to speak publicly about the topic. The Manchester Arena postponed concerts by the pop group Take That scheduled from Thursday through Saturday.
Pop concerts have been a terrorism target before. Most of the 130 dead in the November 2015 attacks in Paris were at the Bataclan concert hall.
Manchester itself has seen attacks before, but not this deadly. The city was hit by a huge Irish Republican Army bomb in 1996 that leveled a swath of the city center. More than 200 people were injured, although no one was killed.
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