Senators Say Case Indicates That Problems Persist in Agencies" Data Sharing WASHINGTON - As investigators sought answers to what or who may have radicalized the suspects in the Boston Marathon bombings, leading lawmakers said Tuesday that potentially important clues about at least one of the men might not have been widely shared within investigative circles months before the attack. Emerging from a closed two-hour hearing with three senior law enforcement and intelligence officials, several members of the Senate Intelligence Committee raised new questions about how the F.B.I. and the Department of Homeland Security apparently handled information about Tamerlan Tsarnaev, 26, the suspect who was killed in a shootout with the police on Friday. "I'm very concerned that there still seem to be serious problems with sharing information, including critical investigative information," Senator Susan Collins, Republican of Maine, told reporters. That is troubling to me that this many years after the attacks on our country in 2001, that we still seem to have stovepipes that prevent information from being shared effectively, not only among agencies but also within the same agency, in one case. Senator Saxby Chambliss of Georgia, the committee's ranking Republican, also voiced worries that efforts to break down barriers of communication between federal intelligence and law enforcement agencies after the Sept. 11, 2001, attacks may have started to erode. "There have been some stone walls and stovepipes reconstructed that were probably unintentional," he said. We're going to continue to look at whether or not all the information was adequately shared and given to all the law enforcement agencies. If it wasn't, we've got to fix that. Senator Dianne Feinstein, a California Democrat who heads the panel, said every investigation revealed flaws, but when asked at a briefing after the hearing if the F.B.I. had "dropped the ball," she said, "No." None of the senators would identify what information was not shared adequately or which agencies were involved, but the issue seemed to center on Mr. Tsarnaev's six-month trip in 2012 to Dagestan and Chechnya, predominantly Muslim republics in the North Caucasus region of Russia. Both have been hotbeds of militant separatists. Testifying earlier in the day before the Senate Judiciary Committee, Homeland Security Secretary Janet Napolitano sought to clarify what the authorities knew about Mr. Tsarnaev's trip. He left the country on Jan. 12 and returned on July 17. His flight reservation set off a security alert to customs authorities when he departed, Ms. Napolitano said, in spite of a "mismatch" in the spelling of his name on his airline ticket, his travel document and the passenger manifest of his flight. As a result of "redundancies" in the system, the error was detected, the secretary said, and "there was a ping on the outbound to customs." But when Mr. Tsarnaev returned, more than a year had gone by since the F.B.I. closed a background review of his possible links to extremist groups that had been requested by the Russian government in January 2011. It was determined that he posed no threat. The security alert "at that point was more than a year old and had expired," Ms. Napolitano said. It is not clear, however, that the customs security alert, flagging Mr. Tsarnaev's travel to Russia, was ever passed on to the F.B.I. And even if it had been, it is not certain what the F.B.I. would have done with that information. Once investigators closed the background check, it would have been a violation of federal guidelines to keep investigating Mr. Tsarnaev without additional information, a senior law enforcement official said. Two months after he returned from Russia, Mr. Tsarnaev applied for naturalization. The application prompted Homeland Security Department officials to review a 2009 domestic abuse arrest, and they found he had not been convicted in that case. They also contacted the F.B.I. and learned that "no derogatory information" on him had emerged from an interview that the agency conducted in January 2011. According to federal law enforcement officials, Homeland Security Department officials left the naturalization "pending," without approving it, as a precaution to see if new information would emerge, but they did not open a new investigation. Ms. Napolitano said that a bipartisan bill in the Senate to overhaul immigration would further tighten security, because it would require all passports to be electronically readable, to avoid errors in flight records. More questions surfaced Tuesday evening when House members attended a classified hearing with Ms. Napolitano and Robert S. Mueller III, the director of the F.B.I. Some lawmakers emerged saying they still felt uninformed about many aspects of the case. Representative Michael McCaul, a Texas Republican who heads the House Homeland Security Committee, said he and other members of Congress were frustrated by the lack of answers on why Mr. Tsarnaev's trip to Russia slipped through the cracks. Jeremy W. Peters contributed reporting.