FBI director: Surveillance programs might have prevented 9/11 Updated: 12:14 p.m. Amid ongoing debate about the propriety of U.S. government programs tracking private citizens' phone and internet use, FBI Director Robert Mueller said Thursday that the government might have prevented the 9/11 terrorist attacks had similar surveillance programs been in place in 2001. Mueller, addressing the House Judiciary Committee just months before the end of his 12-year tenure, outlined a sequence of intelligence data that was collected leading up to the attacks, and argued that the controversial programs, which collect telephone numbers and metadata, could have helped national security experts connect the dots relating to the plan -- and even "derailed" it entirely. Before 9/11 there was an individual by the name of Khalid Almihdhar who came to be one of the principal hijackers. He was being tracked by the intelligence agencies... They lost track of him," Mueller said. At the same time, the intelligence agencies had identified an al Qaeda safe house in Yemen. They understood that that al Qaeda safe house had a telephone number but they could not know who was calling into that particular -- that particular safe house. Almihdhar was in San Diego and had been calling the al Qaeda safehouse in Yemen. If we had the telephone number from Yemen, we would have matched it up to that telephone number in San Diego, got further legal process, identified Almihdhar... The 9/11 Commission itself indicated that investigations or interrogations of Almihdhar once he was identified could have yielded evidence of connections to other participants in the 9/11 plot. The simple fact of their detention could have derailed the plan. In any case, the opportunity was not there. "If we had had this program that opportunity would have been there," he added. In recent weeks, the White House has been dogged by the a series of reports detailing the government surveillance programs, the revelation of which have raised questions - and in some cases, inspired outrage - about Americans' right to privacy. The controversy intensified last Sunday when 29-year-old Edward Snowden revealed himself as the source of the reports, his motives for leaking them, and his whereabouts in China to the newspaper The Guardian. Mueller promised Thursday that the FBI is "taking all necessary steps to hold the person responsible for these disclosures" accountable. But he also defended the programs, arguing that they are consistent with the Constitution and the laws of the United States," and are "carried out with extensive oversight from courts, independent [inspector generals], and Congress." "The challenge in a position such as I have held in the last 11 years is to balance on the one hand the security of the nation and on the other hand the civil liberties that we enjoy in this country," Mueller said. One of the things we do insist upon and assure and that is any endeavor we undertake addressing national security is legal. The White House has maintained throughout the controversy that the programs under discussion are legal under the Patriot Act, and that it continues to act in pursuit of a balance between the interests of privacy and national security. "The highest priority of the intelligence community is to understand and to combat threats to our national security," he told Congress Thursday. But we do so in full compliance with the law. We recognize that the American public expects the FBI and our intelligence community partners to protect privacy interests even as we must -- even as we must conduct -- conduct our national security mission. Liberals and libertarians, particularly, have questioned where that line has been drawn, and Rep. John Conyers, D-Mich., the top Democrat on the committee, expressed his fear Thursday "that we are on the verge of becoming a surveillance state." "The Congress and in particular this committee stands at a crossroads," he said. Every day it seems that a new part of the legal architecture put in place to fight this war on terror is exposed.