Russia asked the FBI to investigate the Boston bombing suspect Tamerlan Tsarnaev in 2011, a US law enforcement official has told Reuters.
The FBI said yesterday that its interview of Tsarnaev, following a tip from a foreign government two years ago, and checks of travel records, Internet activity and personal associations, "did not find any terrorism activity" at that time.
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.