The Obama administration is briefing Congress on Thursday on a yearlong review of the intelligence community's handling of last year's deadly Boston Marathon attack.
The review was conducted by the inspector general of the intelligence community, which is composed of the 17 intelligence agencies. It examined whether there were any missed opportunities to share information that could have prevented two ethnic Chechen brothers who immigrated to the U.S. from carrying out the attack.
The government has said there were no intelligence failures that led to the April 2013 attack that killed three people and injured more than 200 others.
In 2011, Russian authorities told the FBI they were worried that one of the suspected bombers and his mother were religious extremists. The Russians were unresponsive when pressed by the FBI for more details. It was only after the 2013 attack that the U.S. intelligence community learned that the Russians withheld some details that might have led to a more thorough FBI investigation.
The Russians told U.S. officials that they secretly recorded a telephone conversation in 2011 in which one of the Boston bombing suspects vaguely discussed jihad with his mother. In another conversation, the mother of now-dead bombing suspect Tamerlan Tsarnaev was recorded talking to someone in southern Russia who is under FBI investigation in an unrelated case, officials have said.
Even if had the FBI received the information from the Russian wiretaps earlier, it's not clear that the government could have prevented the attack.
Republican and Democratic leaders of the House were being briefed Thursday, congressional aides said.
The House Intelligence Committee was reviewing the report but had no separate briefing planned. The House and Senate judiciary committees were receiving briefings on Thursday as well.
President Barack Obama has not yet seen the report, said White House spokesman Jay Carney, who defended the FBI investigation of the Tsarnaev brothers.
Carney said the agency did a thorough investigation of the brothers' backgrounds in 2011, "based on limited information provided by the Russian government," and found no evidence of terrorism activity.
"The FBI did not find any terrorism activity, domestic or foreign," he told reporters traveling with Obama to Austin, Texas.
Tsarnaev died in a police chase after the attack. His brother, Dzhokhar, has pleaded not guilty to 30 federal charges, including using a weapon of mass destruction.
After the attack, the FBI investigated and found nothing that indicated that the brothers had ties to extremists in Dagestan, a turbulent Russian region that has become a recruiting ground for Islamic extremists.
The U.S. has long been worried about this type of domestic attack: when ideologies motivate people who are not tied to any designated terrorist group to commit violent acts.
Russia's reluctance to share information with the U.S. government that could have helped prevent a terror attack on American soil was one of the first major cracks in the relationship between the two countries. Over the past year, U.S. and Russia relations have deteriorated. Russia gave asylum to National Security Agency leaker Edward Snowden. President Barack Obama cancelled a planned security summit with Russian President Vladimir Putin. And most recently, Russia ignored warnings from the U.S. and its allies and annexed the Crimean Peninsula from the Ukraine.