U.S. President Barack Obama says the explosions at the Boston Marathon are being investigated as an act of terror.
In a brief statement at the White House on April 16, Obama called the April 15 bombings "a heinous and cowardly act," but said it was still unclear who carried out the attacks or why.
"What we don't 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 it was an act of a malevolent individual. That's what we don't yet know," Obama said.
"And clearly we are at the beginning of our investigation. It will take time to follow every lead and determine what happened. But we will find out."
It was Obama's second public statement since the explosions at the annual Boston Marathon.
As he had done on April 15, Obama again vowed to bring whoever was behind the explosions to justice.
Three people, including an 8-year-old boy, were killed in the explosions. Officials said more than 170 were injured, and 17 of them were in critical condition.
FBI agent Rick DesLauriers, who is heading the investigation, said the probe would extend beyond Boston and pursue leads "worldwide."
"We will go where the evidence and the leads take us. We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime and we'll do everything we can to bring them to justice," DesLauriers said.
Massachusetts Governor Deval Patrick said that contrary to earlier reports, no unexploded bombs were found. He said the only bombs were those that went off.
The Boston Marathon bombings have been denounced by leaders across the globe
With reporting by Reuters and AFP