The FBI revealed on Friday that they had interviewed Boston Marathon bombing suspect Tamerlan Tsarnaev in 2011, after a foreign government alerted officials that he had possible ties to extremists.
Federal officials vetted Tamerlan Tsarnaev but their probe not produce any 'derogatory' information and the matter was put 'to bed,' a U.S. law enforcement source said.
The revelation is the first indication that Tamerlan Tsarnaev and his younger brother, Dzhokhar, were known to U.S. security officials prior to Monday's bombings, U.S. authorities said.
Suspect: Tamerlan Tsarnaev (left in 2010) was identified by the FBI as a main suspect (right in surveillance video on Monday) in the Boston Marathon bombings. He was killed by police on Friday
Traditional values: While appearing like an all-American 20-something man, Tamerlan said in an earlier interview that he is a devout Muslim who does not drink and upholds traditional values
The government that asked for the investigation was not identified but security experts have speculated that Russia could have issued the request, based on fears that Tamerlan had links to Chechen extremists.
Based on FBI procedure, it is likely investigators performed a background check on Tamerlan and discussed his behavior and international travel with other agencies.
CBS News believes officials would have called Tamerlan in for a sit-down interview and their findings would have been compiled into a report and sent to the requesting government.
Federal authorities determined that there were no conclusive links between Tamerlan and any extremist groups.
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After the deadly attacks on Monday in Boston, the FBI released surveillance footage of the two suspects they believe were responsible for the blasts.
Officials say Tamerlan and his younger brother, Dzhokhar, refugees from the Caucasus region, were the men behind the horrific terrorist attack that took the lives of three and left 176 injured.
Tamerlan, 26, was killed by police early on Friday morning during a shoot-out in Watertown, Mass. His younger brother, 19-year-old Dzhokhar Tsarnaev is still on the loose and is being hunted down in a massive search.
Suspects: Tamerlan Tsarnaev, 26, (right) was killed during an exchange of gunfire with police early on Friday. His younger brother Dzhokhar, 19, (left) is still on the run
Captured on camera: Blurry CCTV images show the brothers (pictured front: Tamerlan and back: Dzhokhar) walking in single file toward the finishing line of the race, approximately 13 minutes before the explosions
The mother of the two suspects, Zubeidat Tsarnaeva, told RT America on Friday that the FBI had been monitoring her oldest son for being a 'leader' in a religious politics movement.
In broken English, she claimed 'he was controlled by the FBI for 3-5 years. They knew what my son was doing. They knew actions, and what sites on the internet he was going.'
'They used to tell me that they were controlling him, he was a serious leader and they were afraid of him,' she claimed.
'He never, never told me that he would be on the side of jihad,' she said.
She said that he became interested in religion about five years ago.
'The FBI, they were scared of him. They are afraid of him because he is a leader, he talks about Islam a lot. They were talking about my son, they told me he was an excellent boy,' she said.
The mother issued a staunch defense of her sons and insisted on their innocence, alleging that the charges against them were part of a setup.