The U.K.'s intelligence service, MI5, is worried it might have missed some red flags about the Manchester attacker, so now it's investigating itself.
British Home Secretary Amber Rudd confirmed the review to Sky News, calling it the "right first step."
At least 22 people, including children, have died, and dozens more were injured after a bomb exploded at the end of an Ariana Grande concert on May 22.
Police identified the attacker as a 22-year-old man born and raised in the U.K. The BBC says authorities were notified of the suspect's "extremist views" multiple times before the attack.
In the week following the attack, police have arrested 16 people in connection with the bombing. Fourteen of them are still in custody.
Authorities are still searching for a blue suitcase that surveillance camera shows a suspect had. Though a member of the North West Counter Terrorism Unit says the public should not be alarmed, saying in a press release: "I want to stress that this is a different item than the one he used in the attack. We have no reason to believe the case and its contents contain anything dangerous, but would ask people to be cautious."
A total of 1,000 people are currently pursuing more than 1,500 leads in the investigation.
Prime Minister Theresa May said Saturday the country's threat level was lowered from "critical" to "severe." This means the number of soldiers placed at key locations to assist police and protect the public will be scaled back.