Police investigating last Thursday's bombings in London have released CCTV images of one of the alleged bombers as he travelled to London that morning.
The images are of 19-year-old Hasib Hussain, who is said to have blown up a bus killing 13 people.
Scotland Yard said a man injured in the bombings died tonight in hospital, bringing the total number of confirmed dead to 54.
The Deputy Assistant Commissioner of the London Metropolitan Police, Peter Clarke, has appealed for the public's help in identifying the movements of all those thought to have been involved in the attacks.
Police have evacuated more houses in the Beeston area of Leeds, where several of the alleged bombers came from.
Detectives are also said to be searching for one man in particular, thought to be a British muslim of Pakistani origin, who they believe was the bomb maker or the orchestrator of the attacks.
He is thought to have had previous involvement with terrorist operations and could have recruited a second group of British suicide bombers.
Police have been also carrying out an intensive campaign today in search of witnesses.
One week on from the attacks, officers have been stationed at bus, tube and railway stations across the city, handing out leaflets to commuters and appealing for information from anyone who might have seen the four bombers.
Police are also searching a house in Aylesbury in Buckinghamshire following a raid by armed officers last night. It is thought the house is linked to a car used by the terrorists.
No explosives have been found at the semi-detached house in Aylesbury, and no arrests were made there.
Suspect quizzed in London
Police at Paddington Green Station in London are continuing to question a suspect whom they arrested in Leeds.
He is being held on suspicion of involvement in acts of terrorism. It has been reported that he is the brother of the fourth, so far unnamed, bomber who died in the explosion between Russell Square and King's Cross underground stations.
Police have a good idea of who that fourth bomber was but are unlikely to name him until further forensic tests have been carried out on the wreckage of the train.
Separately in Leeds, police investigating a suspected bomb factory connected to the London attacks have said material found there is not hazardous.
Up to 600 people who had been kept away from their homes since Tuesday were being allowed to return this morning.
