The British counterterrorism police seized three men on Thursday for offenses related to the bombings in the London transit system on July 7, 2005, in which four suicide bombers killed themselves and 52 passengers.
The arrests were the first in Britain in connection with the attack and rekindled speculation about whether the plot had extended beyond the four bombers.
Two of the men, ages 23 and 30, were arrested around 1 p.m. at the airport in Manchester, in northwestern England, as they were preparing to board a flight to Pakistan. A third man, age 26, was arrested at a house in Leeds three hours later, the police said. Several of the July 7 bombers had close links to Leeds. The British police routinely do not release names of suspects until charges are filed.
The arrests in the case, Britain's worst peacetime attack, were presented by the police as evidence of their efforts since the attacks to establish whether the bombers, who exploded backpack bombs on three subway cars and a double-decker bus, had accomplices or worked for some shadowy mastermind. The announcement renewed speculation about whether the bombers could have acted alone.
An Egyptian chemist who had known one of the bombers in England was held for several weeks in Egypt not long after the bombings as a suspect in the case but was eventually released.
M.J. Gohal, a security analyst in London who is executive director of the Asia-Pacific Foundation and who has been following the case closely, said that the issue of who masterminded the July 2005 attack probably still remained a puzzle for the British authorities.
He said that the ages of the three men arrested on Thursday indicated that they were probably not the major planners, but instead "co-conspirators," perhaps on the periphery of the plot.
He said he concluded from following the case that "the security services have always believed there were more involved than the four suicide bombers," and added: "But they've never caught the mystery men, the men who recruited them, provided the money, the technical assistance. They've always hit a brick wall on that."
The police moved in on Thursday at a delicate time in an array of counterterrorism inquiries. Six men are currently on trial after failed bombings in London on July 21, 2005.