At least 20 people were killed and possibly "hundreds" of others were injures after one or more loud bangs were heard Monday night at an Ariana Grande concert at Manchester Arena in England, multiple law enforcement told NBC News.
Law enforcement sources in both Britain and the United States told NBC News there were possibly two explosions. There was no immediate information on what kind of explosions occurred, and the sources stressed that the information was preliminary and subject to change.
At Least 20 Killed After Reports of Explosion at Manchester Arena 3:24
Greater Manchester Police said only that there were "a number of confirmed fatalities and injuries" as hundreds of fans fled the arena. Emergency crews rushed to the scene after the possible blasts, which were first reported about 10:40 p.m. (5:40 p.m. ET).
Multiple senior U.S. intelligence officials who are monitoring British authorities told NBC News that preliminary reports indicate that a single explosion took place outside the arena on the southwest side opposite the train station. The explosion occurred as the concert ended, catching people as they exited.
U.S. officials said initial reports from the scene indicated that a number of the casualties might have been caused by a stampede of concert-goers.
New York City counterterrorism police said they were monitoring developments.
People gather outside Manchester Arena and station in Manchester, England, on Monday night. Peter Bendicho
"Ariana is okay," a representative said. "We are further investigating what happened."
Likewise, Bianca Landrieu, the Boston hiphop star known as Bia, who also performed, tweeted: "Guys we are okay!!!"
FollowB I A ⚡️ ✔@PericoPrincess
GUYS WE ARE OKAY !!! THANK YOU WE LOVE YOU6:19 PM - 22 May 2017
British Transport Police said officers were at the arena, which sits atop the Manchester Victoria transit station. All lines to Manchester Victoria were closed, National Rail said in a statement. Northern Railway said the station had been evacuated.
Police: 'A Number of Confirmed Fatalities' at Manchester Arena7:05
Ivo Delgado, who was attending the event, told NBC News that the concert had just ended when "I just heard a loud bang."
"People started screaming and going to the other side of the arena," said Delgado, who said he saw at least one person with blood on his face.
Steve Rotheram, mayor of the Liverpool City Region, tweeted that his two daughters had been in attendance and were safe.
"But I fear for others," he said.