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 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.
In the past week, Russian authorities turned over to the United States information it had on Tamerlan and his mother, Zubeidat Tsarnaeva. The Tsarnaevs are ethnic Chechens who emigrated from southern Russia to the Boston area over the past 11 years.
Even had the FBI received the information from the Russian wiretaps earlier, it's not clear that the government could have prevented the attack.
In early 2011, the Russian FSB internal security service intercepted a conversation between Tamerlan and his mother vaguely discussing jihad, according to U.S. officials who spoke on condition of anonymity because they were not authorized to discuss the investigation with reporters.
The two discussed the possibility of Tamerlan going to Palestine, but he told his mother he didn't speak the language there, according to the officials, who reviewed the information Russia shared with the U.S.
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 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.
Nobody was available to discuss the matter early Sunday at FSB offices in Moscow.
Officials: No sign 'Misha' tied to Boston bombing
Washington • U.S. officials say investigators have found no evidence that a conservative Muslim friend of Tamerlan Tsarnaev had any connection to the Boston Marathon bombing.
Tsarnaev is one of two suspects in the bombing. He died in a shootout with police.
Family members have said he grew up religiously apathetic but hardened his Islamic views in 2008 or 2009 under the influence of a Muslim convert, known to the family as Misha.
Two U.S. officials close to the investigation say the FBI has identified an individual believed to be Misha. The officials would not say whether the FBI has spoken to him but say they've found no ties to the attack or terrorism in general.
The officials spoke on condition of anonymity because they were not authorized to discuss the case.