The hostage-taker shot dead in Texas after a stand-off at a synagogue was known to the UK security services.
It is understood Malik Fisal Akram, from Blackburn, had been investigated by MI5 in 2020 after the receipt of intelligence.
Following an investigation that lasted over a month, it was concluded that he did not present a terror threat.
Akram, who has connections to Manchester, was then listed as a ‘closed’ subject of interest.
The 44-year-old was shot dead on Saturday at Congregation Beth Israel in Colleyville, after a siege that lasted several hours and saw him hold four hostages held in the building.
He could reportedly be heard ranting and demanding the release of a Pakistani neuroscientist jailed for trying to kill US army officers in Afghanistan.
The hostages were eventually freed unhurt and Akram was shot dead by the FBI.
Since then it has emerged that he was served with an exclusion order in Blackburn following the 9/11 attacks, after being branded a 'menace' for perpetually ranting about the atrocity.
He was said to have repeatedly told a magistrates court usher ‘you should have been on the ****ing plane’.
It has now emerged that in 2020, MI5 received intelligence that prompted an investigation into Akram to see whether he posed a threat.
That was considered internally to be a mid-level investigation, meaning he was not deemed a top-priority confirmed threat, but that intelligence needed looking into to see whether he was. It concluded that he was not a terror threat at the time.
He was added to a list of thousands considered a ‘closed’ subject of interest.
It is not clear what intelligence prompted the investigation or how long exactly it lasted.
The news also comes after two teenagers were arrested in South Manchester over the weekend in connection with the siege.
They remain in custody and counter-terror police have not confirmed their suspected offences.
