The U.S.-trained chemist who police believe is the mastermind behind last week's London transit attacks has been captured, Egyptian and Western intelligence sources tell ABC News.
Magdy Elnashar, 33, who authorities believe helped build the bombs, was taken into custody in suburban Cairo, Egypt. Elnashar had left England two weeks before the bombings, and British authorities had initiated a worldwide manhunt for him.
Police say it was Elnashar who helped the bombers set up their bomb factory in Leeds.
Elnashar's capture came as British authorities released the first surveillance photo of one of the bombers in the hours before the attacks.
Hasib Hussain, 18, is seen carrying the backpack that exploded on a double-decker bus two-and-a-half hours later.
Hussain was described by Britain's top police official as just a foot soldier.
"What we've got to find now is the people who trained them, who built their bombs," said Ian Blair, commissioner of London's Metropolitan Police.
British authorities also identified a fourth bomber as a Jamaica-born man with a pregnant wife in England and a mother living in the United States.
U.S. authorities tell ABC News that Lindsey Germaine had been in the United States within the past two years, and the FBI is now investigating contacts he made in Ohio and New Jersey.
The FBI had also joined the search for Elnashar because he attended North Carolina State University in 2000.
But the best lead now is Elnashar himself. Officials in Cairo tell ABC News that state security officials have already begun to question him with British agents in attendance.