LONDON (Reuters) - A suicide attack at a pop concert in Manchester that killed 22 people in May might have been prevented if the security services had responded differently to intelligence in the months before the attack, a government report has found.

FILE PHOTO: Flowers, messages and tokens are left in tribute to the victims of the attack on Manchester Arena, in central Manchester, Britain May 26, 2017. REUTERS/Stefan Wermuth/File Photo

Salman Abedi, a 22-year-old Briton born to Libyan parents, blew himself up at the end of a show by U.S. singer Ariana Grande in the deadliest militant attack in Britain for 12 years. His victims included seven children.

A government-commissioned report by David Anderson, the former independent reviewer of terrorism legislation, found security services were passed two pieces of information on the bomber earlier this year.

The report said security services did not consider the intelligence terror-related at the time, but now says it was “highly relevant”.

“It is conceivable that the Manchester attack in particular might have been averted had the cards fallen differently,” the report said.

The finding follows a review of the roles of the security services in four attacks in London and Manchester between March and June this year that left 36 innocent people dead.

Three of the six attackers were known to the security services, but only person was under active investigation, the report said.

Overall, it said Britain’s security services had performed well amid a growing threat from Islamist militants.

“It is not the purpose of the internal reviews, or of this report, to cast or apportion blame. But though investigative actions were for the most part sound, many learning points have emerged,” the report said.

Britain has thwarted nine plots in the last 12 months, Prime Minister Theresa May’s spokesman said on Tuesday.

Interior minister Amber Rudd told parliament the intelligence services and counter-terrorism police are currently carrying out over 500 live investigations, up a third since the beginning of the year and are investigating over 3,000 people.

The review found that Abedi was one of a small group of former suspects of interest whom Britain’s security services were considering investigating further.

A meeting was due to be held to discuss the potential threat on May 31 - nine days after the attack on the Manchester Arena.