Text messages between Tamerlan Tsarnaev's mother and a relative suspected of involvement in extremist groups that mentioned the young man's interest in "jihad" were not turned over to the FBI when Moscow requested the bureau to look into the background of the bomber.

Fox News:

Russia withheld a crucial piece of information from the U.S. before the Boston bombings, U.S. officials say, bolstering a concern that distrust between the two governments erased an opportunity to avert the disaster.

In 2011, Russia sent an alert to the Federal Bureau of Investigation about alleged bomber Tamerlan Tsarnaev, prompted in part by text messages between his mother and a Russian relative. The texts suggested Tsarnaev was interested in joining militant groups that Russia blames for attacks in the Caucasus region, according to U.S. officials briefed on the investigations.

U.S. officials call these text messages the most important in a series of missed signals between the two countries. One U.S. official characterized at least one of the text messages as generally discussing jihad, but without any specific mention of terrorism plans.

The U.S. officials say they learned about them roughly a week after the April 15 bombings. Several officials say such precise information would have led to a deeper examination of Mr. Tsarnaev, who died a few days after the bombing in a police confrontation. His brother and alleged accomplice remains in custody.

The information Russia withheld "would have allowed the bureau to open an investigation where you could track [Tsarnaev's] communications," said House Intelligence Committee chairman Mike Rogers (R., Mich.). "To me, that's where the ball really got dropped."

Previous terror plots in the U.S. exposed lapses in data-sharing among U.S. agencies, and the official Boston review could still uncover such instances. But so far in the Boston bombing, U.S. officials say, it appears that intelligence-sharing went most awry between the U.S. and Russia.

It may "appear" that the intelligence sharing with Russia "went awry" because that's how the FBI wants it to appear. The fact that the text messages would have presented a "probable cause" situation that would have allowed the FBI to investigate Tsarnaev more thoroughly doesn't mean that the feds would have done anything.

We already knew that the Russians were extremely reluctant to share their sources and methods with the US. And it's not even clear that Moscow believed Tamerlan Tsarnaev to be much of a threat, although local Dagestan authorities evidently tried to track the bomber's movements while he was in the province.

This smacks of more fanny covering by the FBI. They are concerned that an investigation into the bombing will show them to be less than vigilant when it comes to keeping track of potential extremists in the US. But given what the Russians provided us as far as intelligence on Tamerlan, the bureau appears to have acted appropriately.