Al-Awlaki, who would become the first American targeted for death by the CIA, eventually was killed last September in Yemen by a U.S. drone strike.

“I really want to get to the bottom (of this),” said Republican Rep. Frank Wolf, chairman of the committee that has oversight of the FBI. The committee was holding a hearing Wednesday on the Webster report on the FBI’s intelligence failures leading up to the Fort Hood massacre. Al-Awlaki exchanged 19 emails with Maj. Nidal Hasan, accused of murdering 13 in the shooting.

Wolf noted Wednesday that the Webster report makes no mention of the 2002 incident and the FBI’s role in the cleric’s release.

“We’re going to send a letter on this. If we can, we’re going to get a hearing, and if we have to, we may even subpoena the thing," he said.

Mark Giuliano, the FBI's assistant director for national security, testified Wednesday that the FBI knew in advance that he was making his way back to the United States, though he didn't explain how.

Al-Awlaki was detained at New York City's JFK airport because a customs database flagged him based on an outstanding arrest warrant. Giuliano, under intense questioning by Wolf, also admitted there were discussions between an FBI agent and the U.S. attorney in Colorado about the U.S.-born cleric’s re-entry and the warrant.

“Yes, sir, there was a dialogue, as there always will be,” Giuliano replied. “If a case agent has a case on somebody that is coming into the country, the system is triggered and set up so that there will be a call to that case agent.”

Former FBI agents say there are only likely two explanations: The bureau let the cleric into the country to track him for intelligence, or the bureau wanted to work with him as a friendly contact.

During Wednesday's hearing, Giuliano could not explain a significant time discrepancy. Al-Awlaki was being held in the early-morning hours of Oct. 10, 2002, when FBI agent Wade Ammerman told customs agents that "the warrant ... had been pulled back." But that couldn't have happened while al-Awlaki was in custody, since it was only 5:40 a.m. in Colorado where the arrest warrant originated and where the courts had yet to open for the day.

In fact, documents show the warrant was still active at that time and was only vacated later that day.

The FBI has consistently maintained that the arrest warrant was pulled because the case against the cleric was weak, and it has suggested the timing, coming on the same day the cleric re-entered the U.S. at New York City's JFK airport, was coincidental. Foxnews.com