(CNN)MI5, the United Kingdom's domestic spy agency, missed an opportunity to prevent the Manchester Arena bombing, an inquiry into the terror attack has found according to a report in British news agency PA Media.
At least 22 people were killed in the attack at an Ariana Grande concert in Manchester, England, on Monday, May 22, 2017.
The final report of a public inquiry led by chairman John Saunders and released Thursday found that the attack might have been prevented if MI5 had acted on two key pieces of information regarding bomber Salman Abedi.
The information was assessed by MI5 and not found to be terrorism-related, but an officer has admitted that they did consider one detail to contain a potentially urgent national security concern.
However, the issue was not immediately addressed with other colleagues.
"The delay in providing the report led to the missing of an opportunity to take a potentially important investigative action," Saunders wrote in his report.
"Based on everything the Security Service knew or should have known, I am satisfied that such an investigative action would have been a proportionate and justified step to take. This should have happened.
"Although I accept that Salman Abedi demonstrated some security consciousness and that this might have affected the efficacy of the investigative action that I have identified, there was the real possibility that it would have produced actionable intelligence."
Abedi detonated the bomb that killed himself and 22 concertgoers, and injured hundreds more -- many of them children and young people -- as they left Manchester Arena after an Ariana Grande concert.
His younger brother Hashem Abedi, 22, was in Libya at the time of the attack, but was arrested shortly after the bombing and extradited back to the UK in 2019.
In March 2020, he was found guilty of 22 counts of murder, one of attempted murder and one of conspiracy to cause an explosion and jailed for a minimum of 55 years.