WATCH: Fan’s Video Shows the Moment Bomb Explodes at Ariana Grande Concert

A video posted to Twitter by an Ariana Grande fan shows the moment a bomb exploded at the Manchester Arena in England following the pop star’s concert Monday night.

The explosion can not be seen, but is heard. You can watch the video above.

Another video showed the moment of the explosion from outside the arena:

That video shows the outside of the arena. A bright light can be seen in the left corner of the screen followed by a bang. Gregory posted on Twitter that he was waiting outside the arena waiting to pick up his girlfriend and her sister.

At least 19 people have been killed and about 50 injured at the Manchester Arena in England after an “explosion” was reported during an Ariana Grande concert Monday night, the Greater Manchester Police say.

“This is currently being treated as a terrorist incident until police know otherwise,” the police department said in a statement.

Witnesses said a loud explosion was followed by screams, panic and a stamped of people trying to leave the crowded building, which is one of the largest indoor arenas in the world.

Ariana Grande was not among those injured, her representatives said. The incident reported about 10:30 p.m. local time, after Grande left the stage and houselights came on, while people were beginning to exit the arena. About 20,000 people were in attendance at the sold-out show, including many teenagers and young people who came to see the pop star perform. The blast occurred in a public area just outside the arena and the “security perimeter.”

North West Ambulance, the local medical service, said it has taken 59 casualties from the Manchester Arena to various local hospitals, and has also treated a number of “walking wounded” at the scene.

Details about the victims have not yet been released, but reports have indicated that children, including young girls, are among the victims. The Greater Manchester Police said on Twitter, “An emergency number is available for those who are concerned about loved ones or anyone who may have been in the area – 0161 856 9400.”

The North West Counter Terrorism Unit is treating the incident as a possible terrorist incident and is investigating, the BBC reports.

The investigation is ongoing, Greater Manchester Police said.

“We are currently treating this as a terrorist incident until we know otherwise. We are working closely with the national counter terrorism policing network and UK intelligence partners,” Chief Constable Ian Hopkins said in a statement. “This is clearly a concerning time for people but we are doing all we can working with local and national agencies to support those affected and gather information about what has happened tonight. As you will understand we are still receiving information and updates so will provide more details when we have a clearer picture.”

Hopkins added,” I want to thank people for their support and would ask them to remain vigilant and if they have any concerns report them in confidence to us on the Anti-Terrorist Hotline 0800 789321. It is important people avoid the area so that we can effectively deal with the incident.”

You can follow updates on the incident at the link below: