Messages and floral tributes are seen in Albert Square in Manchester, northwest England on May 23, 2017, in solidarity with those killed and injured in the May 22 terror attack at the Ariana Grande concert at the Manchester Arena. Twenty two people were killed and dozens injured in Britain's deadliest terror attack in over a decade, which officials now say could have been prevented.

Messages and floral tributes are seen in Albert Square in Manchester, northwest England on May 23, 2017, in solidarity with those killed and injured in the May 22 terror attack at the Ariana Grande concert at the Manchester Arena. Twenty two people were killed and dozens injured in Britain's deadliest terror attack in over a decade, which officials now say could have been prevented. / Ben Stansall/AFP via Getty Images

Britain's domestic intelligence agency didn't act quickly enough on information that could have helped prevent a 2017 suicide bombing that killed 22 people at an Ariana Grande concert, an inquiry found Thursday.

Retired judge John Saunders, who chaired the inquiry into the Manchester Arena attack, said the MI5 failure to act swiftly led to "this significant missed opportunity." He had previously criticized the arena's staff and local police for failing to identify the bomber as a threat.

The suicide bomber, 22-year-old Salman Abedi, detonated a bomb in the foyer of the arena at the end of the concert as fans left the show on May 22, 2017. More than 100 people were injured, including children and young people.

After the bombing, Ariana Grande's tour was suspended until early June. In a letter to fans, Grande vowed to return to Manchester and wrote that she would think of the people affected by this tragedy "for the rest of my life."

Saunders said MI5 could have acted on its intelligence by stopping Abedi at the Manchester Airport when he returned from Libya four days before the attack, as well as other opportunities.

For example, in 2014, Abedi had been a subject of interest to MI5, but he was deemed low-risk and his case was closed. Authorities didn't refer him to the government's counterterrorism program, Saunders said.

The evidence and intelligence MI5 witnesses provided were not made public.

The Thursday report was the third and final volume of the inquiry into the attack. The first volume came out in June 2021, and the second came out in November 2022. The inquiry began in October 2019.

"Gathering covert intelligence is difficult – but had we managed to seize the slim chance we had, those impacted might not have experienced such appalling loss and trauma," MI5 Director General Ken McCallum said in a statement. "I am profoundly sorry that MI5 did not prevent the attack."

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Tags: suicide bombing  manchester arena  British intelligence