The 2011 conversation worried the Russians so much that they asked the U.S. to investigate Tamerlan Tsarnaev. Russian officials told the FBI only that they had concerns that Tamerlan and his mother were religious extremists and gave no additional information. U.S. officials learned of the wiretap within the last week, according to ABC News.
In another conversation, Zubeidat Tsarnaeva, 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 said.
These conversations are significant because, had they been revealed earlier, they might have been enough evidence for the FBI to initiate a more thorough investigation of the Tsarnaev family.
It was not immediately clear why Russian authorities didn't share more information at the time. It is not unusual for countries, including the U.S., to be cagey with foreign authorities about what intelligence is being collected. After receiving the narrow tip from Russia in March 2011, the FBI opened a preliminary investigation into mother and son - but the scope was very limited under the FBI's internal procedures.
After a few months, they found no evidence Tamerlan or his mother were involved in terrorism. The FBI asked Russia for more information. After hearing nothing, it closed the case in June 2011.
In the fall of 2011, Russian officials contacted the CIA with the same information. Again the FBI asked Russia for more details and never heard back. At that time, however, the CIA asked that Tamerlan's and his mother's name be entered into a massive U.S. terrorism database.
Two years later, authorities say Tamerlan and his brother, Dzhohkar, detonated two homemade bombs near the finish line of the Boston Marathon, killing three and injuring more than 260.
Tamerlan was killed in a police shootout and Dzhohkar is under arrest. Dzhohkar Tsarnaev is being held at Federal Medical Center (FMC) Devens, a federal prison for male inmates requiring specialized or long-term medical or mental health care. ABC News reports the 19-year-old is in a small cell with a steel door.
Analysis of the bombs found they were likely triggered by a toy car remote. This design is not popular with al Qaeda, which suggests the suspects did more research or had outside training to make them.
Zubeidat Tsarnaeva has denied that she or her sons were involved in terrorism. She has said she believed her sons have been framed by U.S. authorities.
Dzhohkar told FBI interrogators that he and his brother were angry over wars in Afghanistan and Iraq and the deaths of Muslim civilians there.
Family members have said Tamerlan was religiously apathetic until 2008 or 2009, when he met a conservative Muslim convert known only to the family as Misha. They said Misha steered Tamerlan toward a stricter version of Islam.
U.S. investigators believe they have identified Misha, but it's not clear if there's any connection to the Boston bombings.
Meantime, the suspects' father Anzor Tsarnaev says he is postponing a trip to the U.S. due to poor health. He told the Associated Press that he is "really sick" and his blood pressure had spiked. He had said earlier that he planned to travel from Russia to the U.S. with the hope of seeing his younger son and burying his elder son.
The Associated Press and ABC News contributed to this report.
