The GMP tweeted Monday that officers from a counter-terrorism unit are continuing to work on the investigation with US law enforcement and that two men were taken into custody for questioning on Jan. 26.
Manchester police said one of the men was released the next day and that the second man was released Monday, Jan. 31.
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Because British police do not release names and details of detainees unless they are charged, no information about the men is known. Police also did not say what investigators may have learned from the men.
"Communities defeat terrorism and the help and support we get from the public is a vital part of that," the GMP said in a statement Monday.
So far, British police are known to have detained at least six people for questioning related to the Colleyville incident.
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The FBI identified the Congregation Beth Israel hostage-taker as 44-year-old Malik Faisal Akram, a British citizen. The FBI has called the Jan. 15 incident “a terrorism-related matter” targeting the Jewish community and previously said it appeared Akram acted alone. The investigation into the incident is ongoing.
British media, including the Guardian and the BBC, have reported that Akram was investigated by the domestic intelligence service MI5 as a possible “terrorist threat” in 2020, but authorities concluded he posed no danger, and the investigation was closed.