Law-enforcement officials say they have no doubt that the explosions near the finish line of the Boston Marathon on Monday afternoon were bombs, possibly placed in mailboxes, garbage cans, backpacks or hidden in some other fashion. Officials at the scene say two people are dead and some 100 injured, including an 8-year old.

As rescue workers, bystanders, and runners rushed to try to help the wounded in the immediate aftermath, Boston limited airport traffic and subway service, fearing further attacks. Several cities, including New York and Washington D.C. put their own police forces on high alert.
But officials seemed to have few clues about who was behind the attack. âWe still do not know who did this, or why, and people shouldn't jump to conclusions before we have all the facts," President Obama said from the White House. "But make no mistake, we will get to the bottom of this."
Officials confirmed that they were only beginning to gather evidence. âEverything right now is guesswork,â says one senior law-enforcement official who was being briefed on the details as they were unearthed by investigators on the ground. Almost any group given over to radical violence is currently viewed as suspect, from homegrown anarchists to foreign jihadists. (It is wise in these cases to remember that the 1995 bombing of the Federal Building in Oklahoma City and the bombing at the Atlanta Olympics in 1996 were carried out by Americans who espoused extreme right-wing causes.)
âA bomb goes off at the spectator side of the finish line where everybody is standing, then a few seconds later a second bomb goes offâitâs pretty simultaneous,â says this official. âItâs the maximum number of spectators and itâs Patriots' Day in Boston.â Whoever is behind it, âthis will be remembered as âthe Marathon attack,ââ said the official, speaking on background, and those who perpetrated it will consider it âvery effective and very successful.â

This law-enforcement official notes that the manner of the attack suggests it may have been Al Qaeda inspiredâif not Al Qaeda directed. According to this official, the first reports about the construction of the bombs indicates they may have been built similarly to those described by Al Qaeda on its Internet manuals for terrorist attacks. Individuals or small groups have, in the past, tried to carry out bombings based on those plans.
Boston authorities played down reports that a Saudi national who suffered injuries at the scene has been arrested. At this point, police are questioning anyone and everyone who may have been at the scene, they say.
In New York, according to Deputy Police Commissioner Paul Browne, as many as 100 of the Critical Response Vehicle (CRV) police cars often seen on drills around the city and always kept at the ready, were put in motion for immediate deployment to landmarks, hotels and other possible targets of terrorist attack. "These are some of the precautions we are taking until we can learn more," said Browne. Inspections were stepped up in the subways as well.
In Washington, the streets around the White House were closed to foot traffic, and a spokesman for the Washington D.C. Police Department confirmed the force was on a âheightened alert.â
âThis is going to reverberate far and wide,â said the same law-enforcement official talking on background. He noted the increased security concerns for the upcoming London marathon.