The U.K.’s counter-intelligence agency MI5 missed a “significant” opportunity to stop a terror attack at an Ariana Grande concert, an inquiry into the incident found. Islamist extremist Salman Abedi killed 22 people and injured hundreds more with a suicide bombing at the Manchester Arena in northwest England on May 22, 2017. In the months leading up to the attack, MI5 was given intelligence on two occasions about Abedi that “transpired to be relevant to Abedi’s plan,” according to Sir John Saunders, the chairman of a three-year investigation into the disaster. “There was a significant missed opportunity to take action that might have prevented the attack,” Saunders said Thursday. He added that while it’s impossible to know if Adebi’s plot could have been averted, “there was a realistic possibility that actionable intelligence could have been obtained which might have led to actions preventing the attack.”