Two U.S. officials briefed on the Boston marathon investigation say the Russian government contacted the FBI and the CIA separately in 2011 with concerns about Tamerlan Tsarnaev, one of the men authorities say was behind the attacks.

One of the officials says the CIA was contacted by Russia in the fall of 2011. Officials say Russia contacted the FBI in early 2011.

The officials spoke on condition of anonymity because they were not authorized to speak publicly about the ongoing investigation.

The FBI said its investigators found nothing to suggest Tsarnaev was part of an extremist group and shared that information back.

Tsarnaev died in a police shootout.

(AP)