The U.S.-born extremist, tied to 26 terrorism cases, would later be killed last year by a U.S. drone strike in Yemen.
A U.S. House panel held a hearing Wednesday on the Webster report, which outlines FBI intelligence failures leading up to the 2009 Fort Hood shooting in which 13 people were killed. The report showed the shooter, Maj. Nidal Hassan, had exchanged 19 e-mails with Awlaki. However, the Webster report made no mention of Awlaki's 2002 detention, The New York Post reported.
"I really want to get to the bottom [of this]." Said Rep. Frank Wolf, chairman of the committee overseeing the FBI.
Mark Guiliano, the FBI assistant director of national security, confirmed there was a discussion as to whether to allow Awlaki's re-entry. Former FBI agents told the Post Awlaki could have been released for two reasons: He was allowed in the country so agents could track him, or the FBI wanted to work with him as a contact.
"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," Guiliano said.
Notable deaths of 2014 [PHOTOS]