Timers Used in Blasts, Police Say; Parallels to Madrid Are Found – New York Times

LONDON, July 7 – Investigators searching for clues in the attacks here said Thursday that the three bombs used in the subway apparently were detonated by timers, not suicide bombers, and that a fourth device may have been intended for a target other than the city bus that it destroyed.

Senior police officials said they had not received a message claiming responsibility for the attacks from any group, and had made no arrests. But officials immediately drew parallels between the London bombings and the ones that struck commuter trains in Madrid 16 months ago, which were carried out by a Qaeda-inspired cell.