FBI interviewed Boston bombing suspect in 2011

Warren Strobel, Mark Hosenball
FBI interviewed Boston bombing suspect in 2011

The FBI interviewed suspected Boston Marathon bomber Tamerlan Tsarnaev in early 2011, following a tip off that he was 'a follower of radical Islam'.

The tip, by a foreign government also said he was preparing to leave the United States to join underground organisations.

The FBI said its interview two years ago of Tsarnaev and his family, along with checks of travel records, Internet activity and personal associations, "did not find any terrorism activity" at the time.

But the revelation is the first evidence that the Tsarnaev family came to US security officials' attention after they emigrated to the United States about a decade ago, and it could raise questions about whether the government missed potential warning signs about the behavior of two brothers.