Why Russia Warned the FBI About Tsarnaev ... and why the FBI didn't investigate aggressively By Rob Quinn, Newser Staff Posted Apr 23, 2013 3:13 AM CDT Updated Apr 23, 2013 6:23 AM CDT 44 comments Comments In this May 4, 2009 photo, Tamerlan Tsarnaev, left, fights Lamar Fenner of Chicago during the 2009 Golden Gloves National Boxing Tournament. (AP Photo/The Salt Lake Tribune, Rick Egan) (Newser) – The Russian tip to the FBI about Tamerlan Tsarnaev two years before the Boston bombings was a result of his frequent visits to a mosque in Dagestan known for producing extremists, Time reports. Tsarnaev came to the attention of Russian security forces after becoming a regular at the Salafist mosque during a 2011 visit. "There wasn’t enough time [in 2011] to come to any conclusions about the extent of his involvement [in Islamist extremism]," a source tells Time. "So we asked our American colleagues to follow up." While sources say Tsarnaev was never observed making contact with insurgent leaders, he very likely heard sermons that pushed "the idea that America and Israel are the axis of evil," a source says. After receiving the tip, the FBI interviewed Tsarnaev and searched its databases before quickly closing the case; Tsarnaev returned to Dagestan for an extended trip the following year—a trip that has become a "key thread" in the bombing investigation. The FBI's 2011 moves are now being heavily scrutinized, but the FBI shouldn't be expected to aggressively pursue every tip from Russia's FSB security service, current and former security officials tell the Daily Beast. The service has been criticized for being used as a tool to attack the Russian regime's political opponents, and there doesn't seem to have been any indication that Tsarnaev posed a threat to the US. "The FSB is mad at a lot of Chechens," says former CIA director Michael Hayden. "Not all of them are terrorists, and even fewer of them are dangerous to the United States."