LONDON—The London bombs that exploded Thursday morning weighed less than 10 pounds each and had to have been placed by more than one individual, police concluded Friday.
Beyond that, piecing together the evidence promised to be a long, arduous task.
Police called it "combing the city by fingertip" and noted the hardships of attempting to study every piece of wreckage from four explosions—three underground and one on a usually busy city street—while trying to remove the dead.
The challenge investigators face perhaps is summed up best in the efforts now under way far underground near King's Cross station.
There are 500 yards of dark tunnel between the safety of an exit and the bodies still trapped in a train that the second bomb destroyed. Rescuers described the heat in the tunnel as almost unbearable, its structural soundness is questionable and the wreckage is daunting. Emergency workers must fight through the twisted remains of the train to find the victims' bodies.
Andy Trotter, British Transport Police deputy chief constable, said progress was being made.
"We've been able to assess that there do not appear to be any more living in the tunnels," he said. "Now we have to go back in and remove the bodies, and continue the investigation. I will not be drawn into guessing how long it might take."
Officials said their top priority was to capture those responsible, and pleaded with the public for tips and leads.
Sir Ian Blair, the head of the London metropolitan police, noted that even seemingly insignificant information could be important to the success of what's being called the United Kingdom's biggest manhunt ever.
"We're appealing to anyone who knows anything," Blair said, noting details such as a neighbor who hasn't returned home, someone who seemed to spend a lot of time working in his garage or an abandoned storage shed.
London Mayor Ken Livingstone added, "Don't feel shy. It may be a memory from a few weeks ago. But it may be decisive."
The bombing death toll passed 50 and was expected to continue to rise as the slow, delicate work of studying wreckage that was spread across London continued.
Police said they'd ruled out the possibility that the bombings were the work of a single individual, as the timing would have been impossible. Each bomb was near the doors in the underground trains, where commuters congregate and luggage often is stored.
Police and other experts also said the bombs were unlikely to have been detonated remotely by cell phones_ the method used in the commuter train bombings last year in Madrid, Spain—as cell phones work poorly on the London Underground. The bombings bear other similarities to the Madrid bombings, however: commuter trains, during rush hour and without warning.
Police acknowledged media reports that an agitated man was checking a package at his feet just before the bus explosion. They said they didn't know if he was involved in the bombing, or even whether a suicide bomber was involved.
They're also unable so far to explain why more people—21 so far—died in the King's Cross bombing than in each of the others, guessing that maybe the trains were more crowded, the tunnel tighter or "we were just a bit less lucky in some spots," Blair said.
Paul Cornish, the head of the international security program for the London research center Chatham House, said such answers would be the result of slow, steady investigation.
"This doesn't look to be a particularly involved plan—simple bombs, hardly exact timing," he said. "It could have been as simple as four friends eating breakfast in central London, then agreeing to head off and look for buses and trains. There may not have been much planning, and there may have been only a few people involved."
As for specifics, Jochen Schiller, an expert on video surveillance at Berlin's Free University, said police were unlikely to find anything poring over video records.
"There's simply too much information to be any help," he said. "There are 3 million people each day riding the London Underground, and almost everyone carries a purse, a backpack, a briefcase, a suitcase. Beyond that, how difficult is it to hide a small package under a shirt or jacket? They are very likely to have captured the bombers on camera, but it is not so likely they will realize it."
Ian Cuthbertson, a Scottish-born counterterrorism expert at the World Policy Institute in New York, a research center, said the bombs appeared to be small and basic, without shrapnel. While he noted that police should be able to determine what the explosive is soon, if they haven't already, others said such a rudimentary bomb was difficult to trace, as ingredients were easily available.
(c) 2005, Knight Ridder/Tribune Information Services.
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