The FBI has confirmed it investigated whether at least one of the Boston Marathon bomb suspects was a follower of "radical Islam" including interviews with Tamerlan Tsarnaev and family members.
In a statement, the FBI said a "foreign government" asked the FBI for information on Tamerlan Tsarnaev.
This request was based on information he had "changed drastically since 2010 as he prepared to leave the United States for travel to the country’s region to join unspecified underground groups".
Both suspects were born in Kyrgyzstan.
The request stated that it was based on information that he was a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States for travel to the country’s region to join unspecified underground groups.
The FBI checked... for such things as derogatory telephone communications, possible use of online sites associated with the promotion of radical activity, associations with other persons of interest, travel history and plans, and education history. The FBI also interviewed Tamerlan Tsarnaev and family members.
The FBI said it had not found any terrorism activity, domestic or foreign, and those results were provided to the foreign government in the summer of 2011.
It said the FBI requested but "did not receive more specific or additional information from the foreign government".
Detectives in Boston are looking further afield as they piece together their case against Marathon suspect Dzohkhar Tsarnaev.
The uncle of Boston bombing suspect Tamerlan Tsarnaev described his recent visit to Dagestan in Russia and his great shock at the attacks.
Both men were enrolled in a school in Dagestan, a neighbouring region that was drawn into Chechnya's violence during the 1990s.