Summary Barack Obama has vowed that whoever is responsible for blasts will feel the full weight of justice.
WASHINGTON (AP) - President Barack Obama, responding to the explosions at the Boston Marathon, says the United States does not know "who did this or why" but vowed that whoever is responsible "will feel the full weight of justice."
He said: "We will find out who did this and we will hold them accountable."
Obama made his remarks Monday evening from the White House about three hours after two explosions detonated near the marathon s finish line. At least two people were killed and 50 injured in the blasts.
Obama has been in touch with federal law enforcement and Massachusetts officials in the aftermath of the explosions.
The Secret Service reacted cautiously to the blasts, expanding the security perimeter around the White House.
Meanwhile, a law enforcement official says cellphone service has been shut down in the Boston area to prevent any potential remote detonations of explosives.
Authorities have not identified what caused the explosives that erupted at the finish line of the Boston Marathon. The official was speaking on condition of anonymity because the investigation was ongoing.
The explosions have killed two people and injured at least 23 others.
On the other hand, police in Los Angeles, New York City and London are stepping up security following explosions at the Boston Marathon.
Los Angeles County Sheriff s spokesman Steve Whitmore says the department has opened an emergency operations center, increased patrols for transit and other critical areas including the Los Angeles Dodgers baseball game Monday night
Chief NYPD spokesman Paul Browne said critical response teams are deployed around the city until more about the explosion is learned. Officials are stepping up security at hotels and other prominent locations.
British police also say they are reviewing security plans for Sunday s London Marathon. It s the next major international marathon. A London Metropolitan Police spokesman says police are working with marathon officials to review security plans.
