U.S. officials say Anwar Al-Awlaki has operated around the fringes of al Qaeda for nearly a decade.
He counseled three of the 9/11 hijackers and earlier this year traded a series of Internet messages with accused Major Nidal Hasan. After the shootings Awlaki praised Hasan as a hero.
The imam has always denied terror ties holding himself out as a spiritual counselor for Muslims.
"There's always this association between Islam and terrorism when that is not true at all," he told the Washington Post in 2001. "I mean Islam is a religion of peace."
But, CBS News correspondent Bob Orr reports that intelligence sources say evidence shows Awlaki is now "a significant part of al Qaeda in the Arabian Peninsula" and he has recently become "more of an operations guy."
Special Report: The Christmas Day Terror Attack
In the months before the attempted bombing of Northwest Flight 253, sources say Awlaki and suspect Umar Farouk Abdulmutallab had communications. And Abdulmutallab told federal investigators that he met face to face with Awlaki in Yemen as part of his indoctrination.
Investigators still can't say exactly how big of a role Awlaki played in the plot. And Abdulmutallab - who was "talkative" right after his arrest - has now stopped cooperating.
But, sources say the suspect has already provided a wealth of intelligence.
Abdulmutallab says he got the explosives in Yemen and said he knew of no other planned attacks. But, Abdulmutallab says he was isolated from other brothers while training in Yemen to keep him from knowing too much about other operatives and other potential plots.
While most of his story has checked out, sources say some of the names of associates that he's provided have turned out to be aliases.
Meanwhile, the people who know Abdulmutallab are still struggling to understand what happened.
Muhammad Al Anasi heads the school the suspect recently attended in Yemen.
"I am now confused because when he was here he was very polite, extremely polite," Al Anasi said. "It is a very big surprise that he did what he wanted to do."
While Abdulmutallab recovers from his burns in a federal lockup, Awlaki remains free - but he's a marked man. A Yemeni airstrike apparently just missed him last week. Intelligence officials say he survived.
More coverage from CBSNews.com:
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Obama to Get Report on Abdulmutallab
Bomb Plot Exposed Lack of Intel "Urgency"
Official: We Knew Al Qaeda Planned "Christmas Surprise"
U.S. Intel Lapses Helped Abdulmutallab
Friend Says Abdulmutallab Was Not Extremist in London
Yemen, North Africa: Terrorism's New Home
Yemen Raids Al Qaeda Hide-Out; 1 Arrested
Opposition Grows to Transferring Gitmo Detainees to Yemen
Dick Cheney: Obama Stance "Makes Us Less Safe"
Democrats Say GOP Playing Politics on Bombing Attempt
Obama: "Systemic Failure" Allowed Attack
Roommate: Abdulmutallab Shunned Women
Abdulmutallab's Missing Months in Yemen
TSA Still Vexed by Explosives Screening
Tracing Bomb Suspect's Journey to Detroit