The Federal Bureau of Investigation was unaware that Tamerlan Tsarnaev traveled to Russia for six months because his name was misspelled, Sen. Lindsey Graham (R-S.C.) told Fox News on Monday morning.

"He went over to Russia, but apparently when he got on the Aeroflot plane, they misspelled his name, so it never went into the system that he actually went to Russia," Graham said. "The reason we didn't know he went to Russia is because the name was misspelled."

In 2011, Tsarnaev was interviewed by the FBI at the request of a foreign government. Law enforcement officials told the AP that the Russian FSB intelligence security service gave information about Tsarnaev to the FBI. The bureau interviewed Tsarnaev and relatives and found no terrorist activity. Tsarnaev traveled to Russia the next year and stayed for six months.

On Sunday, Graham told CNN that the FBI may have dropped the ball in the case by not tracking Tsarnaev when he traveled overseas. Sen. Chuck Schumer (D-N.Y.) agreed, asking, "Why wasn't he interviewed when he came back?"