This story has been updated.
President Obama said that the people or groups responsible for the two explosions on Monday afternoon at the Boston Marathon would “feel the full weight of justice.”
During a press conference with reporters late Monday evening, Obama said that he was briefed by FBI Director Robert Mueller III, along with Homeland Security Secretary Janet Napolitano. Obama also briefed senior members of Congress on the situation, and noted that it was a day when partisanship should be put aside.
Rick DesLauriers, FBI special agent in charge of the Boston field office, told reporters Monday evening that the FBI would take the lead role in the investigation into the incident.
A White House official speaking on background said earlier that Obama also spoke with other members of his senior staff, including recently appointed Homeland Security adviser Lisa Monaco. Obama directed his administration to provide whatever assistance is necessary in the investigation and response to the blasts.
Though federal law enforcement officials told CNN that they were considering the incident as a terrorist attack, Obama stopped short of classifying it that way and said his team was “continuing to monitor and respond to the situation as it unfolds.”
He told reporters: “We still do not know, who did this, or why, and people shouldn’t jump to conclusions until we have all the facts.”
Rep. Bill Keating, D-Mass., a member of the House Homeland Security Committee, said his office has been told that officials in Boston have discovered two unexploded bombs, one in a hotel he declined to name in Copley Square, near the Marathon finish line.
Keating, in a phone interview with the Boston CBS affiliate, WBZ-TV, said the two bombs that exploded near the finish line and the two bombs that did not explode are signs of “coordinated attacks” against an iconic event.
In a statement, House Speaker John Boehner expressed his condolences to the grieving families and gave thanks “for the professionals and Good Samaritans who prevented further loss of life.”
Vice President Biden was on a gun control-related conference call when he learned of the explosions, according to The Washington Post. “Our prayers are with those in Boston,” the paper quoted Biden as saying.
Immediately following the incident, FBI investigators were on the scene setting up a command post in a nearby hotel, according to a local report.
The Homeland Security Department released a statement late Monday evening from Napolitano, where she said her staff along with other Federal, state and local officials were "providing any support necessary in this ongoing investigation." She encouraged the "public to be vigilant," and said they should take direction from state and local officials.
Members of the Massachusetts National Guard were dispatched to the site. More than 400 members of the Guard were helping keep the running route clear during the marathon.
The Federal Aviation Administration implemented a Temporary Flight Restriction until further notice. Earlier reports said that combat aircraft from the Air Force were en route to Boston, but Pentagon officials later told CBS News that the U.S. Northern Command stood down that order. However U.S. Army North said in a Facebook post that its Defense Coordinating Element Region 1 was in the area monitoring the situation.
Officials from the Bureau of Alcohol, Tobacco, Firearms and Explosives were also said to have been on site. Attorney General Eric Holder directed the full resources of the Justice Department to be deployed to investigate the blasts, according to multiple reports.
The Navy confirmed on Monday that it was sending a three-member bomb disposal unit from Naval Station Newport, R.I, to Boston after receiving requests from state officials, the Associated Press reported.
The Washington Post reported that Washington, D.C., was on alert. Other major cities including New York and San Francisco, were also on high alert.
Bob Brewin contributed to this report.