LONDON — British anti-terrorist police now think the mastermind of Thursday’s multiple bombings fled the country even before four explosions on the transportation system killed at least 52 persons.
A massive manhunt was under way for the people who actually planted the bombs, and for the bomb maker.
Police sources also revealed their working hypothesis that between two and four men began their attacks from just one station, even though three bombs shattered train cars on three separate metro lines.
In Washington, the State Department said it has concluded that at least one American was killed in the blast, despite initial reports that there were no U.S. fatalities.
“We have reason to believe that the individual was in harm’s way and has not turned up or otherwise made contact with his friends and family members in London,” said department spokesman Tom Casey.
Citing privacy laws, Mr. Casey would not identify the victim, but CNN reported that relatives of Michael Matsushita, a 37-year-old New York City native, have been told by British police that they think he was among the victims.
London police sources also privately said they concurred with a recent statement by the city’s Metropolitan Police Chief Lord John Stevens that the bombers were “most probably British-born” and fully conversant with British values and idiosyncrasies.
A few seconds before the explosions the bombers likely walked calmly out of King’s Cross station. Experts on Islamist terrorism speculated that this station may have seemed especially suitable as it is being radically rebuilt as the hub of Britain’s Eurostar rail link with continental Europe.
Experts have determined the types of explosives used. They are investigating links between this set of bombings and the material used in Madrid last year.
British intelligence officials met this past weekend with their counterparts from the United States, Canada and about two dozen European countries to discuss potential leads, the Associated Press reported yesterday, citing police.
London newspapers identified a potential suspect as Mustafa Setmarian Nasar — a 47-year-old Syrian suspected of being al Qaeda’s operations chief in Europe and the purported mastermind of the Madrid bombings. U.S. officials said both the United States and Britain were seeking Nasar, who once lived in north London but was thought recently to be in Iraq.
A premature explosion is thought to have caused the bus bombing in London, close to King’s Cross station. The bomber and at least 12 others were killed by the force of the blast, which sheared off half the second deck of the bus.
Witnesses told police they had seen a man nervously fiddling with a bag, an observation first reported Friday in The Washington Times.
Analysts now think it probable that the bomb was being transported away from a bomb scene because it had failed to explode, but then was triggered — possibly accidentally.
It is also possible the bomber deliberately set it off when he thought he was about to be apprehended. The bus driver, after being diverted following the King’s Cross metro bombing, had stopped to ask a policeman which streets he could still use.
In a somber address to the House of Commons, his first since Thursday’s attacks, Prime Minister Tony Blair said it seemed probable that Islamic extremists were responsible for what he denounced as a “murderous carnage of the innocent.”
No specific intelligence could have prevented the strikes, he said.
Officials raised the confirmed death toll, which had stood at 49, to 52 as workers searched for corpses in mangled subway cars marooned in a hot, dusty, rat-infested tunnel, and warned that the body count likely would climb.
In the subway stations yesterday police were out in force. They used stop-and-search powers under the Terrorism Act to frisk people and ask them detailed questions, including their “cultural background.”
The chief of London’s transport police, Paul Crowther, said the main objective of the show of force was to “instill confidence” rather than the expectation of finding terrorists.
David R. Sands contributed from Washington to this article, which is based in part on wire service reports.