Transcript for Investigators Look at Possible Overseas Links to Boston Tragedies
And at the white house, the president was getting up,datedates all day from his team. The release of this photo, we saw today. President obama in the it is wags room with h national security team. The director of the fbi, robert mueller, there on his left. And as we know, the suspect's family have said that they did flee russia, chechnya, area engulfed in a bloody war of resistance. So, could that conflict a world away have played a part in any attack here? Abc's chief global affairs correspondent martha raddatz joining us with more on that. Martha? Reporter: Diane, it is not one of those countries that anyone would really flag as a real enemy of the u.S. But investigators want to know whether the brothers got guidance or financing from oversea overseas, whether in chechnya or anywhere else. Officials have not yet found a smoking gun that would link the men to international terrorists in the attack, but are tapping into every possible source. And while tamerlan tsarnaev and his younger brother dzhokhar spent much of their lives in the united states, dzhokhar and his parents became u.S. Citizens on september 11th of last year, both are ethnic chechens. Chechnya has hosted al qaeda training camps. And chechen terrorists have repeatedly used bombs to attack inside russia. In 2011, a suicide bombing at moscow's airport killed 36 . A year earlier, two bombs struck moscow metro stations during rush hour and killed 40 people. In 2 0009, a bomb blast derailed an express train and killed 26 people. And in 2004, 331 hostages, half of them children, die in a chaotic storming of a school in beslan after it is seized by rebels. A federal law enforcement source items abc news tamerlan spent the first six months of last year in russia. Investigators are now racing to find out what he was doing there. But chechens have never attacked the united states. It doesn't really make sense. Reporter: Both brothers also are muslims. So, investigators are examines whether they were possibly radicalized from abroad or in boston by extremist messages on the internet. They get involved in online internet jihadist forums. They look at a lot of this stuff on websites. Reporter: After decades of battling terrorism, the u.S. Government has an incredible capacity to try to retrace steps or see if there is something they might have missed leading up to this attack. So, they are doing that and finding out everything they can about the brothers.
This transcript has been automatically generated and may not be 100% accurate.