British security services recently investigated the man behind a hostage taking at a synagogue in Texas but deemed he posed no threat, media reports said Tuesday.
US authorities identified the captor as British citizen Malik Faisal Akram, 44, who was shot dead in a 10-hour siege in the small town of Colleyville on Saturday.
Britain's MI5 domestic intelligence agency received information about Akram, who came from Blackburn in northwest England, in 2020, prompting an investigation, several news outlets said, citing unnamed government sources.
But it was shut down again after a little over a month due to lack of evidence that he was a threat, the report added. The agency is now expected to review the investigation.
MI5 keeps tabs on around 3,000 jihadist suspects at any one time, and has investigated up to 40,000 individuals in total.
The four hostages -- including a respected local rabbi, Charlie Cytron-Walker -- were all freed unharmed Saturday night, prompting relief in the United States, where the Jewish community and Biden renewed calls to fight anti-Semitism.
Biden declined to speculate on the motive but appeared to confirm reports that the hostage-taker was seeking the release of Aafia Siddiqui, a Pakistani neuroscientist known as "Lady Al-Qaeda," whose detention has been a cause celebre for jihadists.
At one point the standoff involved 200 local, state and federal law enforcement officers massed around Colleyville.
The incident raised questions about why Akram, whose family said he had mental health problems and was known to have a criminal record, was allowed into the country at the end of last year.
Several British media outlets reported that Akram was banned from a local court in Blackburn for remarks he made to staff about the September 11, 2001 attacks in the United States on the day of the attack.
Two teenagers were arrested on Sunday in the south of Manchester, some 21 miles (34 kilometres) from Blackburn, as part of the US investigation.
Counter Terrorism Policing North West said on Tuesday the pair had been released without charge, and a property in the area searched.
"CTP North West is continuing to assist with the investigation which is being led by the US authorities," said temporary assistant chief constable Dominic Sally.
"Overnight, constructive meetings with colleagues from the United States have taken place."
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