The widow of July 7 suicide bomber Mohammed Sidique Khan was among four people being held last night after anti-terror raids linked to the London bombings.
Hasina Patel, 29, her brother Arshad and two other men were detained under the Terrorism Act over suspected connections to the 2005 attacks in which 52 people died.
Unarmed police swooped just after 7am this morning on addresses across West Yorkshire and the West Midlands.
Properties in Dewsbury, Batley, Beeston in south Leeds, and Birmingham were cordoned off for forensic investigation.
The raids were led by the Metropolitan Police counter terrorism unit, with support from West Midlands and West Yorkshire Police.
Two men, aged 30 and 34, were arrested in Batley and Leeds, while the third man, aged 22, was arrested at 7.25am in Birmingham. They were Arshad Patel, Khalid Khaliq - who is thought to have connections with the Islamic bookshop Iqra in Beeston - and Imran Motala.
All four were taken to Paddington Green police station.
London was thrown into chaos two years ago when four suicide bombers exploded devices in three packed rush hour London Underground Tube trains and a crowded bus.
The perpetrators - ringleader Khan, Shehzad Tanweer, Jermaine Lindsay and Hasib Hussain - all died.