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.
Jim Treacy, the FBI's legal attache in Moscow between 2007 and 2009, said the Russians long asked for U.S. assistance regarding Chechen activity in the United States that might be related to terrorism.
"On any given day, you can get some very good cooperation," Treacy said. "The next you might find yourself totally shut out."
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.
But Ruslan Tsarni, an uncle of the Tsarnaev brothers and Zubeidat's former brother-in-law, said Saturday he believes 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.