WASHINGTON, Aug. 2 (UPI) -- The FBI has concluded it could not have prevented the deadly Boston Marathon bombings, law enforcement officials told The New York Times.
The agency rejected congressional criticism it could have monitored bombing suspect Tamerlan Tsarnaev more closely before the April 15 attacks to see if he became radicalized during his time in the United States, the officials said.
Tsarnaev -- who came to the United States with his younger brother, Dzhokhar Tsarnaev, from the Russian republic of Dagestan about a decade ago -- was killed in a shootout with police four days after he and his brother detonated two bombs at the marathon finish line, authorities say.
The bombs killed 3 people and injuring 264 others, authorities say.
Dzhokhar Tsarnaev was injured in the shootout and was discovered hiding in a boat in a suburban Boston back yard. He was charged April 22 while still in the hospital with use of a weapon of mass destruction and malicious destruction of property resulting in death.
The charges carry potential sentences of life imprisonment or the death penalty.
U.S. lawmakers have argued the FBI should have done a more extensive investigation in response to a 2011 request from a Russian intelligence agency to see if Tamerlan Tsarnaev had been radicalized.
Lawmakers have also said the FBI should have followed up with the older Tsarnaev after he returned from a trip to Russia in 2012.
Russian officials claimed Tamerlan was a follower of radical Islam and was traveling to Russia to join a terrorist group.
But the bureau concluded the agents who told Russian intelligence agents the FBI had no evidence Tsarnaev had become radicalized could not have investigated more deeply anyway because federal laws and Justice Department protocols prohibited it, the Times said.
Agents cannot use surveillance tools such as wiretapping for the type of investigation they were conducting, the newspaper said.
The FBI also concluded if U.S. agents had known Tsarnaev traveled to Russia in 2012, they probably wouldn't have investigated him again in any case because they had no new evidence he had become radicalized, the law enforcement officials told the Times.
The FBI has no plans to appoint a special investigator to examine its procedures, the Times said.
But inspectors general from four federal agencies, including the Justice Department, say they are working together on a separate probe into how Washington handled intelligence before the attack.
The FBI has been cooperating with the inspectors general by giving them investigative files and opportunities to interview agents, the Times said.
An FBI spokesman declined to comment on the Times story, citing the inspectors general's investigation.