Both the CIA and the FBI flagged the deceased Boston bombing suspect over possible terror ties, but he slipped through the fingers of investigators, officials said Wednesday.
The revelations raised fresh questions over why US authorities did not further investigate Tamerlan Tsarnaev, who was killed during a shootout with police last week, and in doing so possibly prevent the attacks.
The CIA asked the top US counterterrorism agency to add Tsarnaev to a terror watchlist more than a year before the bombings, a US intelligence official said.
The spy agency made the move after Russian officials contacted their CIA counterparts in September 2011 about their concerns over Tsarnaev.
His younger brother Dzhokhar, 19, has been charged with federal terror offenses including the use of a weapon of mass destruction in the twin blasts on April 15 that killed three and wounded 264 people at the Boston Marathon's finish line.
Because the older Tsarnaev was a legal permanent US resident, the CIA then shared the information with the appropriate federal departments and agencies, telling them that he may be "of interest" to them, a US intelligence official told AFP.
The data from Russia's Federal Security Service was "nearly identical" to information the FBI received six months earlier in March 2011, the official added.
It included two possible dates of birth, his name in Cyrillic letters and a possible variant of his name.
But a review of his activities turned up nothing deemed actionable.
"No information was incorrectly entered in the watchlisting system, and all the information was shared precisely as the foreign government provided it," the official said.
Tsarnaev's name was added to the Terrorist Identities Datamart Environment, although it was unclear which agency placed it there. The National Counterterrorism Center maintains TIDE, the main US terror database.
The database feeds information to several government watchlists, including the FBI's main Terrorist Screening Database and the "no-fly" list of the Transportation Security Administration.
The FBI's prior review of Tsarnaev had caused him to be added to a separate database.
The CIA shared the data with the National Counterterrorism Center, Department of Homeland Security, State Department and FBI for watchlisting purposes.
The latest disclosure from the CIA reveals that US intelligence agencies may have known more about the elder Tsarnaev's possible extremist links than previously thought.
Lawmakers have expressed growing concern that the case shows continuing problems with government agencies' failure to share information in a fluid manner -- identified as a key problem in the leadup to 9/11 -- more than a decade after the suicide airliner attacks on September 11, 2001.
They are pressing government agencies to find out why US authorities did not monitor Tsarnaev more closely in the time that followed the tip from Russia.
During that time, Tsarnaev made a trip to the restive Russian region of Caucasus, a known hotbed of extremist activities.
A US delegation including FBI agents interviewed the parents of the Boston marathon bombing suspects on Tuesday in the North Caucasus region of Dagestan, officials said.
Asked about Tamerlan's visit to Dagestan, the parents said he "did not make contact with radical Islamists," a local security source told AFP.
The brothers' father Anzor, an ethnic Chechen born in Kyrgyzstan, has repeatedly said in media interviews that his sons were innocent and could not have carried out the bombings. Their mother Zubeidat, an ethnic Avar, hails from Dagestan itself.
New York City Police Commissioner Ray Kelly said earlier that the two brothers were headed to the Big Apple after the bombing "to party" before police stopped them.