WASHINGTON (AP) — A yearlong review of information the U.S. intelligence community had prior to the Boston Marathon bombing found that the investigation could have been more thorough, but the intelligence agencies’ inspectors general said it is impossible to know whether anything could have been done differently to prevent the attack.

The report also said that Russia withheld some information about the bombing suspects until after the attack, but an unclassified version of the report didn’t address what difference that might have made.

The Obama administration briefed Congress Thursday on the intelligence community inspectors general’s findings. The inspectors general examined how the government’s 17 intelligence agencies handled information it had prior to the April 15 attack that killed three people and injured more than 200 others. It explored whether there were any missed opportunities to share information that could have prevented two ethnic Chechen brothers from carrying out the bombings.

Highlighting Russia’s role in potential intelligence failures comes at a time when relations between the two countries are the worst they’ve been since the Cold War era, the deterioration coming over the past year.

Russia’s reluctance to share information with the U.S. government that might have helped prevent a terror attack on American soil was one of the first major cracks in the relationship. Russia gave asylum to National Security Agency leaker Edward Snowden, and President Barack Obama cancelled a planned security summit with Russian President Vladimir Putin. Most recently, Russia ignored warnings from the U.S. and its allies and annexed the Crimean Peninsula from the Ukraine.

Members of Congress have grown increasingly skeptical about the effectiveness of U.S.-Russian cooperation on law enforcement or other matters.

“We will always ask ourselves what more we could have done to prevent this or another tragedy. What we may never understand is why the Russians didn’t share more with us to aid in the FBI’s investigation,” said C.A. “Dutch” Ruppersberger, the top Democrat on the House Intelligence Committee, who has seen the classified version of the report.

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, which the AP first reported weeks after the attack last year. 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 the FBI had received the information from the Russian wiretaps earlier, it’s not clear that the government could have prevented the attack.

Rep. William Keating, a Massachusetts Democrat and member of the House Homeland Security Committee, said what the Russian government did or did not do is less critical to analyze than any missed opportunities by American law enforcement.

“The U.S. should not be reliant on Russia to provide domestic security,” he said. “We should not depend on Russia for the information to make the U.S. safe.”

The inspectors general focused on Tamerlan Tsarnaev’s travel to Russia in 2012 and whether U.S. agencies shared all the appropriate information about his comings and goings. They believe had this information about his travels been shared more widely among U.S. intelligence agencies, it might have prompted further investigation into Tsarnaev.

“Based on all the information gathered during our coordinated review, we believe that the FBI, CIA, (Department of Homeland Security) and the (National Counterterrorism Center) generally shared information and followed procedures appropriately,” the inspectors general said. They recommended areas where coordination and information sharing could be improved, but they said they “found no basis to make broad recommendations for changes in information handling or sharing.”

Russia has been inconsistent in how much information it shares with the U.S. on counterterrorism issues, said David Rubincam, the FBI’s legal attache in Moscow from May 2011 through October 2012. Rubincam has since retired from the bureau. He was interviewed by the intelligence community’s inspectors general over the past year.

“There were things that they would be more forthcoming on and things that they would just not respond to,” Rubincam said of Russian intelligence officials.

Tsarnaev was one of many leads the FBI was pursing based on Russian intelligence, he said. When the Russians asked the FBI in March 2011 to look into Tsarnaev, the FBI did. The bureau also asked the Russians whether they had any more information on Tsarnaev that they could share with the U.S., but Russia was unresponsive.

U.S. intelligence officials in Moscow regularly met with members of Russia’s Federal Security Service about counterterrorism issues, Rubincam said. During these meetings, the Russians would share intelligence concerns with the U.S.

“Certain names come up regularly, but Tsarnaev wasn’t one of them. And I mean never,” Rubincam said of the meetings he participated in with the Russians.

“When it came to my attention what had been withheld from me during my assignment in Moscow, I felt betrayed,” Rubincam said.

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, domestic or foreign.

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 a domestic attack carried out by people motivated by ideology but not tied to any designated terrorist group.