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Source: Russia withheld details about Tsarnaev

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The photos of Tamerlan Tsarnaev were taken by the Cambridge PD in 2009 after his arrest on an assault charge (CNN).

(CNN) — Russia withheld details from U.S. officials about suspicions of Boston Marathon bombings suspect Tamerlan Tsarnaev in 2011, information that could have altered the course authorities followed, a U.S. law enforcement official told CNN.

The Wall Street Journal first reported Friday that while Russia did alert U.S. authorities about Tsarnaev’s possible extremism, it kept out some facts, namely text messages referencing his desire to join a militant group.

However, sources told the paper that the United States also likely would have withheld such details for fear of divulging intelligence sources and methods.

In the texts, Tsarnaev wrote to his mother about his interest in joining the militant movement carrying out attacks against Russia in the Caucasus region, the law enforcement source told CNN.

The Russians did not pass these texts on to American officials when they passed the original intelligence about Tsarnaev, the source said.

The source was not clear on when those texts were eventually handed over.

House Intelligence Committee Chairman Mike Rogers, R-MIchigan, told the Wall Street Journal that the withheld information could have changed the way U.S. officials worked.

Access to the texts “would have allowed the bureau to open an investigation where you could track (Tsarnaev’s) communications,” he said. “To me, that’s where the ball really got dropped.”

In 2011, Russian authorities alerted the United States to concerns that Tsarnaev was becoming increasingly radical. The Russians also raised questions about Tsarnaev’s mother, Zubeidat Tsarnaev, according to several sources.

But the FBI found no evidence of extremist activity and closed the case. The names of both Tsarnaev and his mother were placed in a terror database, however.

Still, Tsarnaev was allowed to travel the next year to a restive Russian region rife with Islamist terror groups, and he returned to the United States after six mysterious months abroad.

Investigators have said they are looking at possible links between Tsarnaev and those groups during his time in the region.