UPDATE 2:40 a.m. EST:
Manchester police confirmed in a statement early Tuesday that the death toll from the attack climbed to 22, with 59 injured. They also said that that the suspected attacker appeared to perish at the site, and their preliminary investigation seemed to indicate there was one lone attacker. This would not rule out that he did so at the order of a terrorist group, or that he had help with planning the attack from a cell in the country.
Police also said that there were children among those killed.
UPDATE 8:16 p.m. EST:
Manchester police say there are 19 confirmed dead, 50 injured, and that they're treating the incident as a terror attack unless they discover evidence otherwise.
Original story continues below.
Police are responding to an incident at an Ariana Grande concert in Manchester, U.K., where reports are that an explosion caused a stampede of fans to exits. There are few confirmed details, but Manchester police have confirmed multiple fatalities. NBC is reporting 20 fatalities.
The Greater Manchester Police confirmed on social media that there were fatalities, but did not detail the source of those deaths.
The statement read, "Emergency services are currently responding to reports of an explosion at Manchester Arena. There are a number of confirmed fatalities and others injured. Please AVOID the area as first responders work tirelessly at the scene. Details of a casualty bureau will follow as soon as possible."
NBC News reported that at least 20 people died, and there were hundreds of injuries.
Fox News reports that the arena held more than 20,000 people and was "jam-packed" at the time of the incident.
There are videos from social media of the aftermath of the reported explosion, with one capturing the scene at the stadium as people stampeded out.
— ABC News (@ABC) May 22, 2017
One report is that the explosion came from a balloon that burst, while there have been rumors of gunshots - these have not been confirmed.
— ️ Vin (@Magnus_Limbus) May 22, 2017