Nineteen people have died following an explosion Monday night at an Ariana Grande concert in northern England, police said. The singer was not injured, according to a representative.

The incident is being treated as a possible terrorist attack. Police said roughly 50 people were injured in the incident, which started at 10:35 Monday night. Bomb-disposal units were seen at the Manchester Arena, where Grande was performing.

There were few further details of what happened during the concert by the American singer, but witnesses reported hearing two loud bangs coming from near the arena's bars.

"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."

Added Oliver Jones, 17: "The bang echoed around the foyer of the arena and people started to run." Video from inside the arena showed concertgoers screaming as they made their way out amid a sea of pink balloons.

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.

Joseph Carozza, a representative from Grande's U.S. record label, said the singer is OK and they are investigating what happened.

The Dangerous Woman Tour is the third concert tour by Grande to support her third studio album, Dangerous Woman. The tour began on February 3 in Phoenix, Arizona, at the Talking Stick Resort Arena.

From Manchester the tour is to move through Europe, including Belgium, Poland, Germany, Switzerland and France, through the summer with stops in Brazil, Chile, Argentina, Costa Rica, Mexico and on to Japan, Thailand, the Philippines, New Zealand, Australia and more.