The wife of 7 July bomber Mohammad Sidique Khan is among four people arrested in connection with the 2005 attacks, which killed 52 people.
Officers arrested Hasina Patel, 29, and two men in West Yorkshire and one man in Selly Oak, Birmingham. Seven addresses are being searched.
The four, aged between 22 and 34, are suspected of commissioning, preparing or instigating acts of terrorism.
They will be questioned at London's Paddington Green police station later.
A search is being carried out of a property in the Handsworth area of Birmingham, believed to be in Leonard Road.
In Selly Oak, police are guarding a student hall of residence involved in one of the raids, but a University of Birmingham spokeswoman said the man arrested was not a student there.
A police lorry took away a silver Peugeot 307 from the Victoria Hall block of flats on Grange Road. A car was also removed from the Handsworth address.
West Midlands Police said the man arrested in Selly Oak was 22 years old.
In West Yorkshire five addresses are being searched - two houses in Penton Road and Dale Street, Dewsbury; two in Tempest Road, Beeston, Leeds; and one in Hayburn Gardens, Batley.
Others charged
Among those arrested was Khalid Khaliq, 34, from Tempest Road in Beeston - the street where 7 July Aldgate Tube bomber Shehzad Tanweer lived.
Tanweer was one of four suicide bombers to mount the co-ordinated attacks in the capital nearly two years ago, which also injured more than 750 people.
Ringleader Khan, 30, killed six people when he bombed a train near Edgware Road station.
Bomber Shehzad Tanweer also lived in Tempest Road in Beeston
A train travelling between King's Cross and Russell Square was also bombed, as was a double-decker bus in Tavistock Square.
The arrests on Wednesday morning followed an intelligence-led operation involving Scotland Yard's counter-terrorism command and units in West Yorkshire and the West Midlands.
Armed officers were not used in the operation.
Police said the inquiry remained a "painstaking investigation" into whether anyone knew what the bombers had been planning and who may have helped them.
Both West Midlands and West Yorkshire forces said they were keeping the affected local communities informed.
Community
Chief superintendent Barry South, of West Yorkshire Police, said the searches could take a matter of hours or days.
"We don't perceive any threat from the addresses that we are searching at this moment," he said.
"It is a high profile investigation but a low key response in terms of how we are policing this operation."
Refusing to speculate on the identity of the people who had been arrested, he said the important issue was to reassure the local community.
He said meetings had taken place with councillors and key community leaders in the area.
Last month the first people to be charged in connection with the bombings appeared at the Old Bailey in central London.
Mohammed Shakil, 30, Sadeer Saleem, 26, and Waheed Ali, 23, of Beeston, Leeds, are accused of conspiring with the four bombers to cause explosions.
The trio, who came before the court via a video link from prison, were remanded in custody until 8 June.
http://news.bbc.co.uk/1/hi/uk/6637917.stm
May Allah hasten her release and i hope they publisize how innocent she is the same way they are publisizing her arrest :rant: