FBI agents are working closely with Russian security officials to reconstruct Tamerlan Tsarnaev's activities and connections in Dagestan during his six-month visit last year, tracking meetings he may have had with specific militants, his visits to a radical mosque and any indoctrination or training he may have received, law enforcement officials said Sunday.
At the same time, the bureau is also still looking for "persons of interest" in the United States who may have played a role in the radicalization of Tsarnaev, 26, and his younger brother Dzhokhar, 19, before the Boston Marathon bombing on April 15, Rep. Mike Rogers, R-Mich. and chairman of the House Intelligence Committee, said Sunday. But Mr. Rogers, speaking on the ABC program "This Week," said "the big unknown" remains what happened in Russia.
Investigators believe it is likely that the Tsarnaev brothers were self-radicalized and got their bomb-making instructions strictly from the Internet. But they are still exploring the possibility that other people in Russia or the U.S. were critical influences, if not accomplices, and officials say it may be weeks before the full picture of their plot is clear.
Officials said they were still examining the conduct of the Tsarnaev brothers' mother, Zubeidat Tsarnaeva, and Tamerlan Tsarnaev's wife, Katherine, 24, who converted to Islam when she married him in 2010.
Amid the scrutiny, Ms. Tsarnaeva and her ex-husband, Anzor Tsarnaev, say they have put off the idea of any trip from Russia to the U.S. to reclaim their elder son's body or try to visit Dzhokhar Tsarnaev in jail. Mr. Tsarnaev told The Associated Press on Sunday he was too ill to travel to the U.S. Ms. Tsarnaeva faces a 2012 shoplifting charge in a Boston suburb, though it was unclear whether that was a deterrent.
On Saturday, the Russian investigative newspaper Novaya Gazeta reported that Tamerlan Tsarnaev, who was slain in the manhunt following the Boston bombing, had sought to join the Muslim insurgency in Dagestan and had been in contact with several rebels who were killed by Russian authorities in late spring of 2012 while he was staying in Makhachkala, the regional capital.
Tamerlan Tsarnaev left Dagestan in July 2012, just two days after a shootout between militants and the police in which several militants were killed, including William Plotnikov, 23, a Russian-born Canadian, and like Tsarnaev, an amateur boxer. Investigators are trying to determine whether Tsarnaev and Plotnikov met, one official said Sunday.
In 2011, Russian officials sent a warning about Tamerlan Tsarnaev's extremist views to both the FBI and the CIA, saying they believed he was coming to Dagestan, a republic in southern Russia, to connect with underground groups. That warning was based on telephone conversations intercepted by Russian intelligence, including one between Tamerlan Tsarnaev and his mother, in which they discussed jihad, Russian authorities have told the FBI.
Experts on the effort by Russian authorities to contain the Muslim insurgency in Dagestan and elsewhere in the North Caucasus region said that if officials were aware of Tsarnaev's arrival in Dagestan in January 2012, he probably would have been under scrutiny throughout his time there.
"He would have been flagged at the airport, when he entered Dagestan and when he went to the mosque," said Jean-Francois Ratelle, a Canadian scholar at George Washington University who is studying the insurgency in Dagestan.
Mr. Ratelle said that in his own research trips to Dagestan, he had been stopped almost every day on the street by police officers checking his registration papers, in part because his beard is seen as a possible sign of religious devotion.
It is unclear how closely the police were tracking Tsarnaev, but his mother, Zubeidat, described at least one instance in which her son was stopped by the police along the beach in Makhachkala, where Tsarnaev's parents live, and brought in for questioning.
"He's like: 'The police came there and they asked for documents,'" Tsarnaeva said at a news conference last week. "They asked him to follow. He was asking them, he was like in shock. He's like: 'What, is there something wrong with me? Am I strange, or don't look like everybody?' "
At the news conference, the brothers' father, Anzor Tsarnaev, acknowledged that Tamerlan had occasionally prayed at a mosque on Kotrova Street in Makhachkala that is known as a gathering spot for Salafists with extremist views. The mosque is just a short walk from the soccer stadium for the local Dynamo team.
Associated Press contributed. First Published April 29, 2013 4:00 AM