At least 22 people are dead and 59 injured after a blast Monday night in Manchester, England, at an Ariana Grande concert, police say.
At a news conference late Monday, Greater Manchester Police Chief Constable Ian Hopkins said authorities are treating the explosion at Manchester Arena as a "terrorist incident" until they have further information.
"This is a very concerning time for everyone," Hopkins said.
Early Tuesday, Hopkins said there are children among the deceased.
Hopkins said a man detonated what appears to have been an improvised explosive device.
Manchester police say more than 400 officers were deployed overnight.
The White House says President Trump, in Israel on the second leg of his first trip abroad since taking office, is being kept up to date on the situation in Manchester.
An emergency number was released for all those concerned about their loved ones or anyone who may have been in the area: 0161 856 9400.
CBS News can confirm the attack was conducted by a suicide bomber, according to two U.S. law enforcement officials. The suspected bomber traveled by Tube to Victoria Station, went to the arena's ticket area and detonated the explosive device as people were leaving the concert. Ball bearings have been recovered. Investigators are tracing the bomber's movements through CCTV.
Body parts of the suicide bomber have been recovered, CBS News has learned.
A source also told CBS News one person was detained in a vehicle but it is not clear what, if any, involvement that potential suspect may have had in the incident.
A representative said.
Late tonight, Grande shared a message on Twitter writing: "broken. from the bottom of my heart, i am so sorry. i don't have words"
Britain's terrorist threat level has been set at "severe" in recent years indicating an attack is highly likely.
Witnesses reported hearing two loud bangs coming from near the arena's bars at about 10:35 p.m. but there were few other details. Emergency vehicles were helping the injured and bomb disposal units were later seen outside the venue.
"A huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the arena," concertgoer Majid Khan, 22, told Britain's Press Association. "It was one bang and essentially everyone from the other side of the arena where the bang was heard from suddenly came running towards us as they were trying to exit."
Oliver Jones, 17, said, "The bang echoed around the foyer of the arena and people started to run."
Police advised the public to avoid the area around the Manchester Arena, and the train station near the arena, Victoria Station, was evacuated and all trains canceled.
"Due to an incident involving the emergency services [Manchester Victoria] has been evacuated," Northern train service officials said. "We will provide further updates when possible."
Zach Bruce, who was at the concert, described the scene on the phone to CBSN.
"It was one loud bang -- it was so loud," Bruce said.
Asked if he would describe it as an explosion, he said yes -- "It was an explosion."
He described people panicking. "I didn't know what was going on," he said.
One Twitter user said she heard an "explosion" from inside the area, where Grande performed moments earlier. There were no immediate details of what happened during the concert.
Video from inside the arena showed concertgoers screaming as they made their way out amid a sea of pink balloons.
One concert goer told BBC Radio 5 Live she was one of the first people to exit the stadium. She said she heard an explosion toward the end of the performance. There were an estimated 20,000 people inside the arena on Monday night.
The U.S. Embassy in London issued a statement Monday alerting U.S. citizens to "maintain security awareness" and seek guidance from local authorities.
"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," the statement read.
U.K. Prime Minister Theresa May said in a statement that officials "are working to establish the full details of what is being treated by the police as an appalling terrorist attack."
"All our thoughts are with the victims and the families of those who have been affected," May said.
Jeremy Corbyn, leader of the Labour Party, responded to reports of the incident on Twitter.
"Terrible incident in Manchester," he said. "My thoughts are with all those affected and our brilliant emergency services."
The Dangerous Woman Tour is the third concert tour by Grande and supports her third studio album, "Dangerous Woman."
Grande's role as Cat Valentine on Nickelodeon's high school sitcom "Victorious" propelled her to teen idol status, starting in 2010. The 23-year-old Grande, with her signature high ponytail, went on to also star in spinoffs that included "iCarly," as she worked to develop her recording career.
The tour began in Phoenix in February. After Manchester, Grande was to perform at venues in Europe, including Belgium, Poland, Germany, Switzerland and France, with concerts in Latin America and Asia to follow.