A Scotland Yard statement added that six properties in London and Lincolnshire have so far been searched as part of the investigation into the murder of Drummer Lee Rigby in Woolwich yesterday.
Search warrants have been executed under PACE at six residential addresses; three in south London, one in east London, one in north London and one in Lincoln. The searches are ongoing.
ITV News has uncovered a video showing Woolwich suspect Michael Adebolajo speaking at a demonstration at Harrow Central Mosque in 2009.
Documents suggest Security Services were trying to recruit Woolwich suspect Michael Adebolajo and had also approached members of his family.
Police in Kenya say they did everything they could to highlight their concerns about Michael Adebolajo.