President Barack Obama says Monday's bombings along the route of the Boston Marathon were an act of terrorism. Officials say three people died in the explosions and more than 170 were injured.
Obama told reporters at the White House the bomb attack in Boston was a "heinous and cowardly act" and for the first time described it as an act of terrorism.
"Anytime bombs are used to target innocent civilians, it is an act of terror," the president said. "What we do not yet know, however, is who carried out this attack or why. Whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual. That is what we do not yet know and clearly we are at the beginning of our investigation."
Watch related video report by VOA's Richard Green
Meanwhile in Boston, federal, state and local investigators briefed reporters at a hotel not far from the scene of the bombings that rocked the city Monday.
The FBI agent in charge of the investigation, Rick Deslauriers, says officials have received “voluminous tips” in connection with the bombings and investigators will follow the trail of evidence wherever it leads.
“This will be a worldwide investigation. We will go where the evidence and the leads take us," Deslauriers announced. "We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime and we will do everything we can to bring them to justice.”
The FBI as well as state and local authorities continue to interview witnesses and conduct forensic analysis of the crime scene, which was at the finish line for the Boston Marathon, which draws elite runners from around the world.
Investigators are asking the public to come forward with video or still photographs they may have taken around the time of the bombings as they search for clues.
Boston Police Commissioner Ed Davis says investigators are already sifting through numerous video surveillance tapes from businesses in the area.
“It is our intention to go through every frame of every video that we have to determine exactly who was in the area. This is probably one of the most well photographed areas in the country yesterday,” remarked Davis.
Deadly bombings in the United States
April 15, 2013: Twin blasts at the Boston Marathon kill at least 3, injure more than 140
September 11, 2001: Hijacked jets crash into World Trade Center, Pentagon and a Pennsylvania field killing nearly 3,000
July 27, 1996: Atlanta Summer Olympics bombing kills 2, injures more than 100
April 19, 1995: Car bomb at Oklahoma City federal building kills 168, injures more than 500
February 26, 1993: Van explosion in World Trade Center garage kills 6, injures more than 1,000
December 29, 1975: Bomb at New York's LaGuardia Airport kills 11, injures 75
September 16, 1920: Bombing in New York's Wall Street area kills 40, injures hundreds
Officials say no one has come forward to claim responsibility for the attack. FBI agent DesLauriers would not comment on reports that police have questioned one man in connection with the case and searched a home in the nearby suburb of Revere.
Massachusetts Governor Deval Patrick said an earlier report that unexploded devices had been found was incorrect. He said the only explosives found were the two that went off.
Patrick urged Bostonians to cooperate with law enforcement authorities.
“Everyone should expect continued, heightened police presence and everyone should continue to personally be vigilant,” he said.
Patrick said an interfaith prayer service is being organized for Wednesday in Boston in the wake of the tragedy.
Longtime Boston Mayor Tom Menino also said the tragedy will bring the city together.
The Boston Marathon
2013 more than 23,000 runners
Last year, runners from 92 countries took part
Race passes through eight cities and towns
Held on Patriots' Day, a state holiday in Massachusetts
Only U.S. marathon that maintains qualifying times
World's oldest still-running annual marathon, first held in 1897
“This is a bad day for Boston, but I think if we pull together we will get through it. We are a strong city and lot of people are willing to work together to make this a better place for all our people,” Menino reassured Bostonians.
The marathon traditionally is held on what is known as Patriot’s Day in Massachusetts, a state holiday that commemorates the first battles of the American Revolution in Concord and Lexington in 1775.
Security has been boosted in several major U.S. cities, including New York and Washington, and condemnations of the Boston bombings have come from around the globe.