NEW : A focus of the briefings was Tamerlan Tsarnaev 's six-month trip to Russia in 2012 that family members said included visits to Chechnya and Dagestan , regions known for radical Islamic insurgency . Senators say no indication yet that the FBI ` ` dropped the ball '' NEW : Republican senators criticized failure of federal agencies to provide information . Legislators criticized the FBI investigation of bombing suspect Sergei Tsarnaev . The FBI investigated him two years before the Boston Marathon bombing .
NEW : Senators say no indication yet that the FBI ` ` dropped the ball '' NEW : Republican senators criticized failure of federal agencies to provide information . Legislators criticized the FBI investigation of bombing suspect Sergei Tsarnaev . The FBI investigated him two years before the Boston Marathon bombing .