Updated

Neither the FBI nor the Justice Department has provided documents or witnesses for an official congressional investigation launched by the House Homeland Security Committee into the American cleric Anwar al-Awlaki, who was killed in a CIA-led mission last Friday, Fox News has learned.

The congressional investigation -- opened in May -- questioned whether the cleric's contacts with three of the five hijackers on American Airlines Flight 77, which crashed into the Pentagon on Sept. 11, 2001, were coincidental or part of the terror plot's development.

The House Homeland Security Committee, led by Rep. Peter King, R-N.Y., is also seeking to learn more about the FBI's contacts with the cleric before and after Sept. 11. For instance, in October 2002, an FBI agent told customs agents at John F. Kennedy International Airport in New York to let the cleric go from federal detention even though there was an active warrant for Awlaki's arrest

An investigation by Fox News' Special Unit entitled "The American Terrorist" showed the Awlaki arrest warrant and the decision to release him from federal custody was likely withheld from the Sept. 11 commission that was convened to review how the Sept. 11 attacks occurred and how to prevent future attacks.

During a hearing before the House Intelligence Committee on Thursday, King demanded answers from FBI Director Robert Mueller.

"Do I have any reason to believe that we're not going to get the information ... involving the FBI's dealings with al-Awlaki and the Justice Department dealings with al-Awlaki?" he asked.
"No and I, quite obviously, I'd go back and check and see what has happened in response to that letter," Mueller said, adding, that the bureau would return a response to King.

King also questioned the cleric's stint as a guest speaker at the Pentagon in February 2002 -- first reported by Fox News -- and the fact the FBI had interviewed the cleric at least four times in the first eight days after Sept. 11 because of his known contacts with the three hijackers. Mueller, whose bureau is run out of the Justice Department, replied that he would have to get back to him.

Even though Awlaki is dead, Homeland Security Committee staffers say they believe the FBI should not be allowed to ignore an official congressional investigation. They note that Awlaki was held in federal custody in 2002, and suggest that had he been prosecuted at the time, acts of domestic terrorism like the 2009 Ft. Hood massacre and the Christmas Day and Times Square attempted bombings -- both which allegedly are linked to Awlaki -- as well as the CIA-led strike that led to his death last week -- might have been avoided.

This is the second time the FBI has apparently failed to respond to a congressional inquiry about Awlaki. In April, Mueller testified on Capitol Hill, where he faced tough questions from Rep. Frank Wolf, R- Va., whose district at one time contained the cleric's mosque in Falls Church, Va.

Wolf said he wanted to know why Mueller had not responded to his request for information -- sent to the FBI in the summer of 2010 -- about the bureau's October 2002 decision to release Awlaki from custody upon his return to the U.S. despite an outstanding warrant for his arrest at that time."

"Could you discuss why the information was not shared with the 9/11 commission and provide the committee with a detailed accounting in the appropriate setting?" Wolf asked.

Mueller said he remembered looking at the warrant, which originated out of Denver, Colo., in the summer of 2002, adding "there was not much more -- not much more and certainly at this time to be done." The FBI director did not elaborate.

Mueller added that if the FBI's material had not provided to the Sept. 11 commission, it was "certainly not by intent," and noted the commission "was appreciative of all the work that we had done to provide them, you know, just about everything that we had in our files."
Mueller said he would get back to Wolf.

When Congressman Wolf’s office followed up in August, staffers say they were told that the FBI director considered the matter "closed."

In response to King's requests on Thursday, a spokesman said the Justice Department and FBI "continue to work on responses to Rep King's letter and FBI officials have been in discussions with Rep. King's staff."

Fox News National Correspondent Catherine Herridge's bestselling book "The Next Wave: On the Hunt for al Qaeda's American Recruits" was published by Crown on June 21st. It draws on her reporting for Fox News into al-Awlaki and his new generation of recruits -- al Qaeda 2.0. It is the first book to full investigate al-Awlaki’s American life, his connections to the hijackers, and how the cleric double crossed the FBI after Sept. 11.