More than 24 hours after a series of terrorist bombs rocked London's public transportation, the investigation into how it all happened is well under way. Hours of closed circuit television footage are being scrutinized, tons of wreckage is being sorted for clues and experts are hustling to analyze tiny traces of explosives. Meanwhile, hundreds of Londoners, most of whom are putting on a brave face in reponse to the terror,  are attempting to return to their daily routines. Transport has returned to near normal service, and commuters are once again decending into Tube stations across the city.

British Prime Minister Tony Blair and London's chief of police have said that the death toll was expected to be over 50 because authorities have yet to account for bodies trapped in an underground train at Russell Square, where emergency workers are having difficulty with recovery due to fears that the tunnel is unsafe. The investigation, meanwhile, is intensifying as resources are freed up from initial emergency response duties.

The search for the perpetrators is happening under tremendous time pressure. After all, just three weeks after the vicious attacks in Madrid in March 2004, police discovered some of the plotters in a Madrid apartment with more explosives. They were apparently planning further attacks. And that is something London wants to avoid at all costs.

"There is a real passion now in the police to make arrests quickly before further attacks can be carried out," Charles Shoebridge, a security analyst and former counterterrorism officer told the Associated Press. "While (the bombers) are at large now, a second attack is very likely, because there's no reason for them not to. They've broken their cover."

But on Friday, London's primary concern -- aside from mourning the 50 known dead and caring for the 700 wounded  -- was getting life back to normal. While it is still not clear whether al-Qaida was indeed behind the attacks, Foreign Secretary Jack Straw said on Thursday that the attacks had the "hallmarks of an al-Qaida related attack."

On Thursday evening, Blair appealed to the British not to be daunted by the attacks. "We know that these people act in the name of Islam," he said in a statement from 10 Downing Street. "But we also know that the vast and overwhelming majority of Muslims both here and abroad are decent and law abiding people who abhor this kind of terrorism every bit as much as we do."

Already, there have been some preliminary results from the investigations. According to one US investigator who declined to be named, evidence from the explosion sites seems to indicate that the bombs were detonated using timing devices. Investigators assume that the bombs -- contrary to those in Madrid over a year ago -- could not have been set off using mobile phones as they frequently don't work in the London subway tunnels. There is, so far, no indication that suicide bombers were involved in the attacks. Authorities and secret service personnel from the US, France, Spain, and Germany are assisting the British in the investigation, according to Home Secretary Charles Clarke. He also emphasized that there were no warnings prior to the attack.

In fact, British intelligence officiers were primarily focused on security at Gleneagles for the opening of the G8 meeting. And, they were rather certain that the terrorist threat was at lower-than-usual levels. In early June, Britain's central intelligence agency, the highly esteemed Joint Terrorism Analysis Center, downgraded the threat of international terrorism faced by the UK from "severe general" (the highest alert state) to "substantial." They made their assessment using all the clandestine and open-source material they had, undoubtedly sifting it through the minds of all their analysts. But still, they got it wrong.

Two hours after the attack, a letter from a group calling itself "Secret Organization -- al Qaida in Europe"  was posted on the Internet claiming responsibility for the attack and saying it had acted because the British "crusader government" was involved in Afghanistan and Iraq. The claim has so far not been authenticated.

The deadly detonations came just one day after London was chosen to host the 2012 Olympic Games. But a British International Olympic Committee member, Craig Reedie, said in Singapore where the IOC was meeting, that the attacks would not affect London's planning for the games. "I can assure you that these terrible acts in no way reduced our resolve to run excellent Olympic Games in 2012," Reedie said. "The worst thing to do is concede to these people."