Instructions: In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Input: Investigators are exploring potential links between Boston Marathon bombing suspect Tamerlan Tsarnaev and an extremist group known as the Caucasus Emirate, sources tell Fox News. 
  
 The purported leader of the separatist and Islamic extremist group is Doku Umarov, a Chechen Islamic militant in Russia whose ordering of numerous attacks on civilians has earned him the nickname Russia's Usama bin Laden. The U.N.'s Al Qaeda sanctions committee has also cited Umarov for his alleged connections with Al Qaeda and other extremist groups. 
  
 The investigation is based on the contents of Tsarnaev's YouTube channel and his trip to Russia in the first half of 2012, which included stops in Dagestan and Chechnya. 
  
 Sources tell Fox that videos deleted from his YouTube account include a “terrorist playlist” and links to Vilayat Dagestan, which is associated with Caucasus Emirate. 
  
 The 26-year-old Tsarnaev was killed early Friday in a shootout with police. His 19-year-old brother, Dzhokhar Tsarnaev, was captured that night. They are suspected of placing two bombs along the marathon course Monday that killed three and injured roughly 180 others. 
  
 On Sunday, a website used by Russia's North Caucasus rebels distance the group from the bombing. 
  
 In addition, an unnamed Russian security source told the Interfax news agency: "At the moment, we have no credible information about the Tsarnaev brothers' involvement with the Caucasus Emirate movement." 
  
 Investigators are now looking for potential ties including Tamerlan’s email traffic, the posting of videos in support of an Islamist objective and whether there was person-to-person contact. 
  
 Sources tell Fox that Caucasus Emirate is one of several groups being investigated. 
  
 Caucasus Emirate was designated a foreign terrorist organization by the State Department in 2011. 
  
 “The group uses bombings, shootings and attempted assassinations to provoke a revolution and expel the Russian government from the North Caucasus region,” according to designation. 
  
 Ambassador Daniel Benjamin, the department’s coordinator for counter terrorism, said the designation was in response to “threats posed to the United States and Russia.” 
  
 “The attacks perpetrated by Caucasus Emirate illustrate the global nature of the terrorist problem we face today,” he also said. “We stand in solidarity with the Russian people in our condemnation of these deplorable terrorist acts.” 
  
 Caucasus Emirate was also listed in March 2011 by the United Nations’ Al Qaeda and Taliban Sanctions Committee. 
  
 Catherine Herridge is an award-winning Chief Intelligence correspondent for FOX News Channel (FNC) based in Washington, D.C. She covers intelligence, the Justice Department and the Department of Homeland Security. Herridge joined FNC in 1996 as a London-based correspondent. ||||| WASHINGTON — With one suspect dead and the other captured and lying grievously wounded in a hospital, the investigation into the Boston Marathon bombings turned on Saturday to questions about the men’s motives, and to the significance of an overseas trip one of them took last year. 
  
 Federal investigators are hurrying to review a visit that one of the suspected bombers made to Chechnya and Dagestan, predominantly Muslim republics in the north Caucasus region of Russia. Both have active militant separatist movements. Members of Congress expressed concern about the F.B.I.’s handling of a request from Russia before the trip to examine the man’s possible links to extremist groups in the region. 
  
 Tamerlan Tsarnaev, who died early Friday after a shootout with the police in Watertown, Mass., spent six months in Dagestan in 2012, and analysts said that sojourn might have marked a crucial step in his alleged path toward the bombings. 
  
 Kevin R. Brock, a former senior F.B.I. and counterterrorism official, said, “It’s a key thread for investigators and the intelligence community to pull on.” 
  
 The investigators began scrutinizing the events in the months and years before the fatal attack, as Boston began to feel like itself for the first time in nearly a week. 
  
 On Monday, the twin bombings near the finish line of the Boston Marathon killed three people and wounded more than 170. The tense days that followed culminated in Friday’s lockdown of the entire region as the police searched for Mr. Tsarnaev’s younger brother from suburban backyards to an Amtrak train bound for New York City. 
  
 Dzhokhar Tsarnaev, 19, was taken into custody Friday night after he was found, bloody and weakened, hiding on a boat in a driveway in Watertown. He was still too wounded to speak on Saturday, said Gov. Deval Patrick of Massachusetts. Special counterterrorism agents trained in interrogating high-value detainees were waiting to question him, according to a law enforcement official. An issue arose about the administration’s decision to question him for a period without giving him a Miranda warning, under an exception for questions about immediate threats to public safety. 
  
 The brothers’ motives are still unclear. Of Chechen heritage, they had lived in the United States for years, according to friends and relatives, and no direct ties have been publicly established with known Chechen terrorist or separatist groups. While Dzhokhar became a naturalized American citizen last year, Tamerlan was still seeking citizenship. Their father, Anzor, said Tamerlan had made last year’s trip to renew his Russian passport. 
  
 The significance of the trip was magnified late Friday when the F.B.I. disclosed in a statement that in 2011 “a foreign government” — now acknowledged by officials to be Russia — asked for information about Tamerlan. The request was “based on information that he was a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States for travel to the country’s region to join unspecified underground groups.” 
  
 The senior law enforcement official said the Russians feared he could be a risk, and “they had something on him and were concerned about him, and him traveling to their region.” Chechen extremists pose a greater threat to Russia than they do to the United States, counterterrorism specialists say, though some of the groups have had ties to Al Qaeda. 
  
 But the F.B.I. never followed up on Tamerlan once he returned, a senior law enforcement official acknowledged on Saturday, adding that its investigation did not turn up anything and it did not have the legal authority to keep tabs on him. Investigators are now scrambling to review that trip, and learn about any extremists who might have influenced, trained or directed Tamerlan while he was there. 
  
 President Obama and Republican lawmakers devoted their weekly broadcast addresses to the Boston attack, with both sides finding a common voice. Mr. Obama also met with his national security team for an update on the investigation. 
  
 “Americans refuse to be terrorized,” Mr. Obama said. “Ultimately, that’s what we’ll remember from this week.” 
  
 Since 1994, Russia and the United States have routinely exchanged requests for background information on residents traveling between the two countries on visa, criminal or terrorism issues. 
  
 Eric Schmitt and Michael S. Schmidt reported from Washington, and Ellen Barry from Moscow. Reporting was contributed by John Schwartz and Julia Preston from New York; Andrew Roth and David M. Herszenhorn from Makhachkala, Dagestan; Peter Baker from Washington; and C. J. Chivers from the United States. ||||| The chairman of the House Intelligence Committee, Rep. Mike Rogers, R-Mich., said on NBC’s Meet the Press Sunday that when Tamerlan Tsarnaev, the Boston Marathon bombing suspect killed Friday in a shootout with police, travelled to Russia in 2012, he may have done so under an alias. 
  
 Tamerlan Tsarnaev’s six-month stay in Russia last year “becomes extremely important” as a key to the investigation of the Boston bombings, Rogers told NBC’s David Gregory. His visit to Russia “would lead one to believe that that’s probably where he got that final radicalization to push him to commit acts of violence and where he may have received training” in terrorist techniques. Rogers, a former FBI agent, said the FBI had questioned Tamerlan Tsarnaev after being given information from a foreign intelligence service “that they were concerned about his possible radicalization.” 
  
 NBC's Adrienne Mong reports from Dagestan with more on what authorities are looking at relating to a trip that Boston bombing suspect Tamerlan Tsarnaev recently took to Russia. 
  
 (That foreign intelligence service is widely thought to be Russia’s.) 
  
 The FBI, Rogers said, “did their due diligence and did a very thorough job” of investigating Tamerlan Tsarnaev, but when the FBI asked for more help from that foreign intelligence service, it got no further cooperation. 
  
 Rogers praised the FBI’s handing of Tamerlan Tsarnaev as “very prudent and very thorough” – and pointed out that the FBI questioned Tamerlan Tsarnaev before his sojourn in Russia. 
  
 But appearing on CNN's State of the Union Sunday, Sen. Lindsey Graham, R- S.C., said Tamerlan Tsarnaev is the kind of person "you don’t want to let out of your sight,” and that it was a mistake for federal authorities to have lost track of him. 
  
 “Either our laws are insufficient or the FBI failed, but we’re at war with radical Islamists and we need to up our game,” the South Carolina Republican told CNN. 
  
 The Tsarnaev family were ethnic Chechens, an embattled Islamic nationality in Russia. They were granted legal permanent residence in the United States in 2007. 
  
 Boston bombing suspect Dzhokhar Tsarnaev, Tamerlan Tsarnaev’s younger brother who was captured Friday night and is being treated in a Boston hospital, became a naturalized American citizen last year. 
  
 Because the Boston marathon bombing suspect is an American citizenp, he cannot be tried as an enemy combatant. A panel of national security experts discusses what lies ahead for the investigation. 
  
 Boston Police Commissioner Ed Davis said on Fox News Sunday that Dzhokhar Tsarnaev is in serious condition and is “in no condition to be interrogated at this time.” 
  
 Scholars have for years pointed to ties between Chechen separatist fighters in Russia and al Qaida and the global jihadist movement. 
  
 The biggest questions for investigators now, said NBC News Justice Correspondent Pete Williams , are why Tamerlan Tsarnaev apparently turned to jihadist views and “where did he get his expertise in explosives? Where did he practice them? It seems really unlikely that these two bombs successfully were detonated without some practice runs. Where did he learn to do that? Where did he practice it?” 
  
 Michael Leiter, the former director of the National Counterterrorism Center and an NBC News National Security Analyst, said it is not atypical for a foreign-born Muslim who has lived in the United States for years to become radicalized at some point and then engage in a terrorist plot. He cited the example of Faisal Shahzad, a Pakistani-born naturalized U.S. citizen who confessed to a plot to bomb Times Square in New York City in 2010. 
  
 Asked whether Dzhokhar Tsarnaev should receive the Miranda warning that he has a right to remain silent before authorities begin to question him, Rogers said, “He’s a citizen of the United States and that brings all of the protections of the U.S. Constitution. Under the public safety exception, however, I do believe that the FBI has a period of time to try to determine what threats there are today – we don’t know if there’s other (explosive) devices, we don’t know if there’s other people (involved in the plot). I think Mirandizing him up front would be a horrible idea. Now it’s my understanding that that’s not going to happen. I’ve had conversations with the FBI….” 
  
 He added, “We don’t need his confession up front. We need the information that he has to make America is safe.” 
  
 In a joint statement issued Saturday, three Republican senators, Graham, John McCain of Arizona, and Kelly Ayotte of New Hampshire, joined by Rep. Peter King, R-N.Y., said the Boston bombing suspect should not be given Miranda warnings. He “clearly is a good candidate for enemy combatant status. We do not want this suspect to remain silent,” they said. 
  
 “We are encouraged our High Value Detainee Interrogation Team (HIG) is now involved and working to gather intelligence about how these terrible acts were committed and possibility of future attacks,” they said, adding that the decision by the Obama administration to not immediately read him the Miranda warning “was sound and in our national security interests. However, we have concerns that limiting this investigation to 48 hours and exclusively relying on the public safety exception to Miranda, could very well be a national security mistake. It could severely limit our ability to gather critical information about future attacks from this suspect.” 
  
 Sen. Saxby Chambliss, R-Ga., the vice chairman of the Senate Intelligence Committee agreed with that assessment, saying “I am disappointed that it appears this administration is once again relying on Miranda's public safety exception to gather intelligence which only allows at best a 48-hour waiting period that may expire since the suspect has been critically wounded.” |||||
Output:
As the Boston Marathon bombing investigation continues, the FBI is really zeroing in on dead suspect Tamerlan Tsarnaev's six-month trip to Russia last year, the New York Times reports. The elder of the Tsarnaev brothers visited two predominantly Muslim republics in the country's north Caucasus region—Chechnya and Dagestan—both of which are home to strong militant separatist movements. Russia had warned the FBI that Tsarnaev was a "follower of radical Islam" back in 2011, but law enforcement officials did not deem him a security risk; now some members of Congress are unhappy at the way the tip was handled in advance of Tsarnaev's overseas trip, considering he may have had connections to extremist groups in the area. It was after that trip that he started posting jihadist videos. As federal investigators rush to review the trip (which Tsarnaev's father says was simply to renew his son's Russian passport) and any extremists Tsarnaev may have connected with in Russia, one former senior FBI official calls it "a key thread for investigators and the intelligence community to pull on." But at the time, the FBI never followed up on Tsarnaev after he returned to the US, because it did not have the legal authority to do so after uncovering nothing of note in its initial investigation. The FBI investigation did, however, prevent Tsarnaev from becoming a US citizen; the Department of Homeland Security opted to hold his petition for further review. Sources tell Fox News that investigators are looking into possible connections between Tsarnaev and the Caucasus Emirate, a separatist and extremist Islamic group whose Chechen leader is known as "Russia's Osama bin Laden." And today on Meet the Press, Rep. Mike Rogers, chair of the House Intelligence Committee, said Tsarnaev may have made the Russia trip under an alias.