Prime Minister Theresa said she will chair a second emergency meeting Tuesday and that Britain's terrorism "threat level" will be reassessed over the coming 24 hours.
May spoke on the steps of Downing Street following the suicide bombing Monday night at a concert in Manchester, which has so far claimed 22 lives and left behind at least 59 casualties. The bombing targeted children and young adults who were attending a concert by U.S. singer Ariana Grande.
The police were said by the PM to have identified the attacker although they have not yet disclosed a name.
May said that the incident was Britain's worst terror attack. She will chair a second meeting of the COBRA (Cabinet Office Briefing Room) committee later Tuesday as part of the government's response to the incident.
The terror threat level, which has remained at its second highest level since 2014, will be reviewed over the course of the coming 24 hours. A "severe" threat level means that an attack is likely.
Greater Manchester Police Chief Constable Ian Hopkins said in a statement earlier, "The priority is to establish whether he was acting along or part of a network."