As the investigation continues into last week's deadly bombings of London's transit system, British authorities have announced they have videos of the four men suspected in the attacks.

Peter Clarke of Scotland Yard's Anti Terrorist Branch, left, and Andy Hayman of the Special Operations department deliver an up-date of Police operations during a Scotland Yard press conference in London
Britain's National Coordinator of Terrorist Investigations, Peter Clark, Tuesday said police have video footage showing the men arriving by train to the Kings Cross subway station shortly before explosions rocked three of the city's subway lines.

Mr. Clark said three of the four suspects in the investigation came from West Yorkshire, near Manchester.  Based on forensic analysis obtained at the blast sites, he said police raided several homes.  One person has been detained in what Mr. Clark described as a rapidly moving investigation.

More than 50 people were killed when the bombers struck the British capital's subway and bus system.  Some 700 others were injured in the attacks.

Some information for this report provided by AP, AFP, Reuters.