The CIA's request came months after the FBI had closed a preliminary inquiry into Tsarnaev after getting a similar warning from Russian state security, according to officials who spoke on condition of anonymity because they were not authorized to discuss the matter.
The disclosure of the CIA's involvement suggests that the U.S. government may have had more reason than it has previously acknowledged to scrutinize Tsarnaev in the months leading up to the bombings in Boston. It also raises questions as to why U.S. authorities did not flag his return to the United States and investigate him further after a seven-month trip he took to Russia last year.
The CIA declined to comment on its role. A U.S. intelligence official said that the agency had "nominated [Tsarnaev] for inclusion in the watchlisting system" and had shared all of the information it had been given by Russia, including "two possible dates of birth, his name and a possible variant."
The official said that the information that Russia provided to the CIA was "nearly identical" to what it had shared with the FBI. U.S. officials said that the warning to the CIA came from Russia's FSB, a successor to the KGB, and that it was based on fears that Tsarnaev was an Islamist extremist who might seek to carry out a terrorist attack in Russia.
Tsarnaev and his 19-year-old brother, Dzhokhar, immigrated to the United States about a decade ago, but their family had ties to Chechnya, a region where Muslim separatists have been engaged in a bloody conflict with the Moscow government for decades. The younger Tsarnaev, who is recovering from gunshot injuries in a Boston hospital, was apprehended days after the marathon bombings and faces multiple terrorism-related charges.
Although police feared he was heavily armed, the younger Tsarnaev had no firearms when he came under a barrage of police gunfire that struck the boat where he was hiding, according to multiple federal law enforcement officials Wednesday.
The FBI declined to discuss what led to the gunfire. Others said the shooting may have been ignited by the chaos of the moment.
The FSB appears to have turned over information on Tamerlan Tsarnaev, including possible birth dates and the spelling of his name in Cyrillic letters, to CIA officials in Moscow in late September 2011.
The information was passed to CIA headquarters on Oct. 4 and relayed roughly two weeks later to the National Counterterrorism Center, an agency that serves as a clearinghouse for threat data and manages the TIDE database.
The revelation of the CIA's role is likely to intensify questions over whether the FBI and other domestic law enforcement agencies missed chances to detect or disrupt the bomb plot.
The older Tsarnaev traveled to Russia on Jan. 12, 2012, less than three months after his name had been placed on the TIDE list. In congressional testimony Tuesday, Homeland Security Secretary Janet Napolitano said that the U.S. authorities had flagged Tsarnaev's departure but not his return.
"The system pinged when he was leaving the United States," Napolitano said at a Senate hearing. "By the time he returned, all investigations had been closed."
Napolitano was referring to the FBI's decision in July 2011 to close its inquiry into Tsarnaev after concluding he was not a threat. U.S. officials have said that FBI decision meant that his name might have come off the database employed by U.S. Customs agents a year later - just days before his reentry into the United States.
The CIA's subsequent involvement in the case complicates that chronology, raising the possibility that Tsarnaev was still on the TIDE list when he returned. If Customs officials had alerted the FBI to his return, the bureau might have found reason to question him further in the months leading up to the attacks.
Instead, the FBI was not notified of his return, and it is not even clear that the bureau was aware that Tsarnaev's name had been added to the TIDE database at the behest of the CIA.
U.S. officials stressed it's not clear that they could have prevented the outcome in Boston.
The elder Tsarnaev "did not come anywhere close to being a selectee" for the U.S. no-fly list, an intelligence official said. Asked what might have changed if his return had been called to the FBI's attention, the official said: "Probably nothing."