"There is no evidence that any other suspects were present at the killing of soldier Drummer Lee Rigby in London last week," a senior Scotland Yard officer has told MPs.
Statements have been taken from 60 "significant" witnesses to the attack, assistant commissioner Cressida Dick informed the UK Parliament's Home Affairs Select Committee, which is chaired by Labour MP Keith Vaz.
"The vicious murder of Drummer Lee Rigby was a terrible reminder of the dangers of violent extremism which can come at any time, from outside our borders or even from within," Vaz said.
She added that 17 addresses and six cars had been searched and police had so far seized 2,649 items of potential evidence, along with an "enormous" amount of digital data and forensic material.
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Twelve people have been arrested over the attack, two have been charged, eight bailed and two released.
Lee Rigby was killed near Woolwich Barracks on May 22 and Michael Adebolajo, 28, and Michael Adebowale, 22, have now been charged with his brutal murder.
British Prime Minister David Cameron has since set up a special task force on tackling extremism and radicalisation in the country.
Speaking in the House of Commons yesterday, Cameron said: "There is nothing in Islam that justifies acts of terror and I welcome the spontaneous condemnation from mosques... When young men born and bred in this country are radicalised and turned into killers we have to ask some tough questions. It is as if for some young people there is a conveyor belt to radicalisation. We need to dismantle this process.