WASHINGTON // Russian authorities secretly recorded a telephone conversation in 2011 in which one of the Boston bombing suspects vaguely discussed militancy with his mother, but the US government received details about the call only last week, officials said.
In another conversation, Tamerlan Tsarnaev's mother, Zubeidat Tsarnaeva, was recorded talking to someone in southern Russia who is under FBI investigation in an unrelated case, they said.
The conversations are significant because, had they been revealed earlier, they might have prompted a more thorough FBI investigation of the Tsarnaev family.
As it was, Russian authorities told the FBI only that they had concerns that Tamerlan and his mother were religious extremists. With no additional information, the FBI conducted a limited inquiry and closed the case in June 2011.
Two years later, authorities say Tamerlan and his younger 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.
The Tsarnaevs are ethnic Chechens who emigrated from southern Russia to the Boston area over the past 11 years.
Russia's FSB internal security service intercepted a conversation between Tamerlan and his mother vaguely discussing militancy in early 2011, according to US officials who spoke on condition of anonymity.
The two discussed the possibility of Tamerlan going to Palestine, but he told his mother he did not speak the language there, according to the officials, who reviewed the information Russia shared with the US.
In a second call, Zubeidat Tsarnaeva spoke with a man in the Caucasus region of Russia who was under FBI investigation. Jacqueline Maguire, a spokeswoman for the FBI's Washington field office, where that investigation was based, declined to comment.
There was no information in the conversation that suggested a plot inside the United States, officials said.
It was not clear why Russian authorities did not share more information at the time. It is not unusual for countries, including the US, to be cagey with foreign authorities about what intelligence is being collected.
Nobody was available to discuss the matter at FSB offices in Moscow early yesterday.
Zubeidat Tsarnaeva has denied that she or her sons were involved in terrorism. She has said she believes her sons have been framed by US authorities.
But Ruslan Tsarni, an uncle of the Tsarnaev brothers and Zubeidat's former brother-in-law, said on Saturday that he believed the mother had a "big-time influence" as her older son increasingly embraced his Muslim faith and decided to quit boxing and school.
After receiving the narrow tip from Russia in March 2011, the FBI opened a preliminary investigation into Tamerlan and his mother. But the scope was extremely 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.
Authorities have said they have seen no connection between the brothers and a foreign terrorist group. 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. Misha, they said, steered Tamerlan toward a stricter version of Islam.
Two US officials say investigators believe they have identified Misha. While it was not clear whether the FBI had spoken to him, the officials said they have not found a connection between Misha and the Boston attack or terrorism in general.