Anti-terror police in Britain have widened their search, as the country comes to terms with news that the four suspected terrorists in the London bombings were home-grown.
Officers raided a home in the market town of Aylesbury, around 60 kilometres northwest of London, but made no arrests and found no explosives.
Authorities are urgently looking for the bomb-maker who would have instructedthe extremists, amid fears that future suicide attackers may have already been armed and trained.
According to one national newspaper, police believe they have identified the mastermind behind the attacks. He is thought to have left the country on the eve of the bombings which left at least 52 people dead.
At Luton station north of London, where the perpetrators boarded a train into the city, officers found explosives in an abandoned car.
There is widespread shock that the four bombers were born and brought up in Britain. At least three of them came from the Leeds area in the north of the country and were of Pakistani origin.
One was described by friends and family as a cricket-loving university graduate with no interest in politics.
Muslim leaders in Britain say their community now faces its most profound challenge yet.