Leeds, England ? Police pursued what they suspect is a mastermind behind London’s terror attacks, raiding a home Wednesday and widening their search to a new area. The top law enforcement official suggested the bombers were “foot soldiers” intent on causing mayhem.

Wednesday night’s raid in Aylesbury, some 40 miles northwest of London and near the city of Oxford, resulted in no arrests but police were searching the house, Scotland Yard said.

As a show of defiance, London’s trademark black taxis and red double-decker buses were asked to pull to the side of the road and workers were urged to take to the streets at midday today for a moment of silence marking the week that has passed since the July 7 terrorist bombings killed at least 52 people.

Details emerged Wednesday about the lives of the four suspected bombers, one of whom was only 19 years old. Another had gone to Pakistan for two months this year to study religion. At least three of the suspects were Britons of Pakistani descent.

“These foot soldiers who have done this are only one element of an organization that is bringing about this kind of mayhem in our society,” Home Secretary Charles Clarke, the country’s top law enforcement official, told the British Broadcasting Corp. “We are looking very, very closely at the relationship between the people who may have committed the offenses and the wider network around them.”

Several officials, including Foreign Minister Jack Straw, have said the attacks bore the “hallmark” of al-Qaida. Two claims of responsibility purportedly from militant Islamic groups have surfaced.

A U.S. government official confirmed Wednesday that Shahzad Tanweer, Hasib Hussain and Mohammed Sidique Khan are thought to have been three of the bombers. The names are being checked to see whether they appear on any U.S. databases. The official spoke on the condition of anonymity because British investigators have not publicly released the identities of the suspected attackers.

Customers and members of the press gather at the fish and chip shop in the Beeston district of Leeds that is owned by Mohammed Tanweer, the father of suspected London suicide bomber Shahzad Tanweer. Shahzad Tanweer is one of three suspected bombers; police on Wednesday were searching for a mastermind of last week's attacks.

Britain’s Press Assn., citing police officials, said Wednesday that police had identified the fourth suspected bomber but no name or details were reported.

Surveillance cameras captured the four as they arrived in the capital 20 minutes before the beginning of the rush-hour explosions.

Police refused to comment on a BBC report that authorities were seeking a fifth suspect.

In London, police continued to search through voluminous evidence from close-circuit TV footage and the grisly scene where the blasts ripped apart three trains and a bus. In and around the northern city of Leeds, home to a large Muslim community, police searched for evidence in sealed-off neighborhoods where three of the four suspects lived.

More than 100 alleged revenge attacks – including the killing of a Pakistani immigrant – have been reported in Britain since the bombings. Police increased protection in Muslim communities.