The explosions that struck the Boston marathon on Monday "appear" to be to a terrorist attack, according to the White House.
"Any event with multiple explosive devices -- as this appears to be -- is clearly an act of terror, and will be approached as an act of terror," the official said in a statement, Politico reported.
"We don’t yet know who carried out this attack, and a thorough investigation will have to determine whether it was planned and carried out by a terrorist group, foreign or domestic," the official added.
Addressing the nation on the attacks, President Barack Obama also urged the American people to show restraint before all of the facts have emerged.
"We don't know who did this or why. And people shouldn't jump to conclusions before we have all the facts," Obama said at the White House briefing room. "But make no mistake, we will get to the bottom of this. And we will find out who did this, we'll find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice."
Boston police commissioner Edward Davis told reporters earlier Monday that two simultaneous explosions occurred near the finish line of the Boston marathon, 50 to 100 yards apart.