A U.S. Senator has revealed that the FBI didn't know Boston Marathon bomber Tamerlan Tsarnaev traveled to the volatile Russian republic of Dagestan last year because his name was misspelled on travel documents.
Anti-terrorism authorities never interviewed 26-year-old Tsarnaev about his visit to the region, which is home to organized extremist Islamist militias who have committed numerous terrorist attacks against Russian authorities and moderate Sufi Muslims.
Russian intelligence tipped off the FBI in 2011 that Tsarnaev might be radicalized and was likely planning a trip to Russia.
FBI agents interviewed and investigated Tsarnaev then, but later closed the case after finding no evidence of 'terrorism activity, domestic or foreign.'
Family ties: This family photo shows the Tsarnaev brothers and their sisters as children. Dzhokhar is seen bottom center and older brother Tamerlan is pictured top center
A look back: Tamerlan, center bottom, is seen as a baby with his father Anzor, left, and mother Zubeidat, center, and uncle Muhamad Suleimanov, right
Strife: The Russian region of Degastan has long had a significant Islamist militant movement that has been responsible for numerous bomb attacks and assassinations
Both Tsarnaev brothers are immigrants with family roots in Chechnya, another Russian region in the north Caucuses marked by Islamist militancy.
Tamerlan was killed after a shootout with police early Friday. Authorities say he likely died after his younger brother ran over him while fleeing in a stolen SUV.
Dzhokhar was dramatically captured Friday night and is being questioned by federal agents at a hospital, where he recovering from what is reportedly a self-inflicted gunshot wound to the neck.
Tsarnaev and his younger brother Dzhokhar then dropped off the FBI's radar entirely until they emerged as suspects in last Monday's bombing at the Boston Marathon that killed three people and maimed dozens of others.
'He went over to Russia, but apparently when he got on the airplane, they misspelled his name, so it never went into the system that he actually went to Russia,' Senator Lindsey Graham told Fox News on Monday.
The South Carolina Republican said he received his information from the assistant FBI director.
Graham had previously said the agency 'dropped the ball' by not tracking Tamerlan Tsarnaev before the attacks. On Monday he softened his tone.
'One of two things happened, the FBI either dropped the ball or our system doesn’t allow the FBI to follow this guy in an appropriate fashion,' Graham said.
Dropping the ball: Lawmakers demanded on Sunday why the FBI hadn't put more flags on Boston bombing suspect Tamerlan Tsarnaev, pictured left in 2010, and right, last Monday, minutes before the attack
In custody: Dzhokhar Tsarnaev, 19, is in critical condition at a Boston hospital after he was discovered Friday evening hiding in a boat in Watertown
Outspoken: New York Sen. Charles Schumer, left, D-New York, and Sen. Lindsey Graham, R-South Carolina, raised questions on CNN over the FBI's follow-up on the elder Tsarnaev brother
'I think once the Russians made the request, the FBI did a good job of looking at him. The reason we didn’t know he went to Russia is because the name was misspelled.'
Much of what Tsarnaev did on his six-month trip to Russia is still a mystery to U.S. investigators.
Neighbors say Tsarnaev spent at least a few weeks in Dagestan.
On Sunday, House of Representatives Homeland Security Committee Chairman Michael McCaul wrote to the FBI and other officials asking why Tamerlan Tsarnaev did not raise suspicions after Russia asked the bureau to investigate him two years ago.
'Because if he was on the radar and they let him go, he's on the Russians' radar, why wasn't a flag put on him, some sort of customs flag?,' McCaul, a Texas Republican, said on CNN's 'State of the Union.’
'And I'd like to know what intelligence Russia has on him as well.'
Sen. Charles Schumer (D-New York) was largely supportive of the FBI’s efforts, but questioned why Tamerlan wasn’t interviewed upon his return from Russia, where he had been for six months in 2012.
‘There were things on his website that indicated that he had been radicalized,’ Schumer said. ‘I think there’s a lot of questions that have to be answered.’
Dwelling: The Tsarnaev brothers lived in this nondescript house in Cambridge, just across the river from Boston
The FBI interviewed Tsarnaev in 2011, shortly after Russia's Federal Security Service asked the agency to look into him as a possible Islamist radical who might soon travel to Russia. It was unclear before yesterday which foreign country had tipped off the FBI.
When contacted, the FBI referred MailOnline to the statement it issued on April 19, saying the FBI’s search into Tamerlan’s records, travel history, and internet use yielded no results.
Meanwhile, the organization has vehemently refuting a claim by the mother of the Tsarnaev brothers who said the bureau had spoken to Tamerlan following the two bombs exploding at last Monday’s marathon.
FBI spokesman Michael Kortan told the Associated Press Sunday that the interviews in 2011 with Tamerlan and family members were the agency’s only contact with the bombing suspect. The Tsarnaevs' parents live in Russia.
Less than a year after the FBI interview, Tsarnaev did in fact travel to the volatile Dagestan region of southern Russia on a six-month trip out of the United States.
Frequent: Tamerlan was said to often visit the Islamic Society of Boston mosque in Cambridge, pictured
Republican Representative Peter King of New York told 'Fox News Sunday' he wondered why the FBI did not take more action after Tsarnaev returned to the United States last year and put statements on his website 'talking about radical imams.'
Tamerlan Tsarnaev was not put on any no-fly list of suspected terrorists, U.S. officials said. But his brush with the FBI did raise concerns when he applied for U.S. citizenship last year, a source close to the bombing investigation said.
Officials of the Homeland Security Department decided to give his application extra scrutiny because of the FBI interview and also due to an allegation against him of domestic abuse on a girlfriend in 2009, the source said. The citizenship application was still under consideration when Monday's bombing happened.
Tamerlan Tsarnaev was killed in a shootout with U.S. police. and his brother Dzhokhar, 19, remained hospitalized in serious condition on Sunday, unable to speak. Three people were killed in Monday's bombing and 176 were injured.
Republican Senator Lindsey Graham of South Carolina said 'the FBI or the system dropped the ball' on the elder Tsarnaev. Graham told CNN that U.S. laws do not allow the FBI to follow up enough even if it does spot danger.
Democratic Senator Charles Schumer of New York told CNN 'there's certainly a lot of questions' about the FBI's handling of the case.
One U.S. counterterrorism official urged perspective. 'If we thoroughly investigated every one of these terrorism tips we get, we'd never get anything done,' he said.
Guarded: Police guard the entrance to Beth Israel Deaconess Medical Center Saturday, where Dzhokhar Tsarnaev, is being treated, rooms away from 11 of the bombing victims
Critical: Tsarnaev, who was arrested Friday night, remains in critical condition under heavy guard after he was apprehended in Watertown
Captured: The FBI wanted poster released last night was updated to show that Dzhokhar was in custody
A senior U.S. law enforcement source said that the number of tips received from Russian intelligence to the FBI each year is 'not that many.'
But nationally, he said, the FBI receives at least 100 terrorism tips a day - from the public, local and state law enforcement, other federal agencies and the intelligence community.
House Intelligence Committee Chairman Mike Rogers, a former FBI agent, defended the agency. The Michigan Republican said the FBI had performed a 'very thorough' review of the older brother in 2011, but then it failed to receive further cooperation from Russia.
'That case was closed prior to his travel, so I don't think we missed anything,' Rogers said on NBC's 'Meet the Press.'
'At some point they (the FBI) asked, is there more clarifying information, and never received that clarifying information, and at some point they have nothing. You can't ask them to do something with nothing,' Rogers said.
But McCaul and King said the handling of Tamerlan Tsarnaev's case looked like it was part of a pattern.
Open investigation: Law enforcement evidence technicians continue to investigate the scene of the Boston Marathon bombings on Saturday
The 26-year-old 'appears to be the fifth person since September 11, 2001, to participate in terror attacks despite being under investigation by the FBI,' the pair said in a joint letter.
They named the others as Anwar al-Awlaki, a U.S.-born cleric and leader of al Qaeda's affiliate in Yemen who was killed in a U.S. drone strike; David Headley, an American who admitted scouting targets for a 2008 Islamic militant raid on Mumbai; Carlos Bledsoe, who killed an Army private outside a military recruiting office in Arkansas in 2009; and Nidal Hasan, who is accused of killing 13 people at Fort Hood, Texas, in 2009.
In addition, Umar Farouk Abdulmutallab, who tried to bring down a U.S. jetliner over Detroit on Christmas Day 2009, had been identified to the CIA as a potential terrorist, the letter said, adding the cases 'raise the most serious questions about the efficacy of federal counterterrorism efforts.'
The McCaul-King letter asked for all information the U.S. government had on Tamerlan Tsarnaev before April 15. It was also addressed to Director of National Intelligence James Clapper and Homeland Security Secretary Janet Napolitano.