British police say they believe four British-born suicide bombers were behind the attacks that killed at least 52 people in London last week.
Police say they have found body parts and personal items of the suspects at the four blast sites. They also have video footage of the four men arriving at London's King's Cross Station shortly before the attacks.
Media reports say the suspects were of Pakistani descent and between the ages of 18 and 30. At least three of the suspects lived in the northern British county of West Yorkshire.
Police raided six homes in the city of Leeds Tuesday, finding what appeared to be a bomb factory in one location, and arresting a relative of a suspect in another.
British Home Secretary Charles Clarke told journalists in Brussels Wednesday, that the attackers may have been working in what he called a "wider community."
Officials have speculated that the bombers had someone providing oversight or expertise who could still be inside Britian.
Some information for this report provided by AFP and Reuters.