FBI Says It Could Not Have Prevented Boston Marathon Bombing: Officials

FBI officials have concluded that the agency could not have done more to prevent April's Boston Marathon attacks, law enforcement officials told The New York Times.

The FBI previously faced criticism regarding how it handled a 2011 request from a Russian intelligence agency to keep tabs on Tamerlan Tsarneav, who would later be accused in the bombing along with his younger brother, Dzokhar Tsarnaev.

The Russian agency suspected that Tsarnaev had been "radicalized" since immigrating to the United States from the Republic of Dagestan, according to the Times.

"Once you're brought to attention by a foreign government, I think you should have a red flag put then, to be taken off later," Sen. Lindsey Graham said on CNN's "State of the Union" in April. Graham stated that the FBI "dropped the ball."

FBI agents did investigate Tsarnaev, and wound up concluding that there was no evidence he had been radicalized.

According to multiple internal reviews examining the investigation, agents were unable to investigate Tsarnaev more thoroughly due to federal law and other restrictions imposed by the Justice Department. The review notes that agents are prohibited from wiretapping on an investigation of that type, according to the Times.

The Agency also came under fire for not following up on Tsarnaev after he returned from visiting Russia in 2012. According to the Times, it's unclear whether the FBI even knew Tsarnaev went to Russia at all.

Since the Boston Marathon attacks, Homeland Security and the FBI have both implemented measures to ensure they will receive notification when a former investigation subject travels overseas. However, an unidentified official who spoke with the Times stated that even if "these adjustments [had] been in existence before the attacks, the outcome would likely not have been any different."

Tamerlan Tsarnaev was killed in a firefight with police four days after officials say he and Dzhokhar set off the two bombs that killed three people and injured more than 200. Dzhokhar Tsarnaev was indicted in June on 30 counts, including using a weapon of mass destruction and bombing a place of public use.