At least 19 people were killed and more than 50 injured after an explosion in the foyer area of a crowded Manchester concert hall, which left hundreds of people fleeing in terror.
Sources said the the initial theory was that a suicide bomber was behind the suspected terrorist attack at the Manchester Arena, with witnesses claiming to have heard an explosion around 10.40pm as a revellers, many young, were leaving. It was feared that the casualty toll may rise.
Police said they were dealing with a possible terror incident and counter-terrorism officials were assessing what caused the explosion. Investigators from the police and the domestic security service MI5 were part of the investigation.
A concert by the American pop singer Ariana Grande was being staged at the time. Footage from inside the arena, which has a 21,000 capacity, shows a crowd containing many young revellers.
The incident comes at a time when Britain has been on a severe terrorist alert, meaning an attack is highly likely.
Initial examination of the scene around the explosion led police to consider whether a suicide bomber was responsible, the Guardian understands. It is one theory being looked into in the early stages of the investigation. NBC have also reported the same early line of investigation.