May 8, 2012 — -- In a stunning intelligence coup, a dangerous al Qaeda bomb cell in Yemen was successfully infiltrated by an inside source who secretly worked for the CIA and several other intelligence agencies, authorities revealed to ABC News.
The inside source is now "safely out of Yemen," according to one international intelligence official, and was able to bring with him to Saudi Arabia the bomb al Qaeda thought was going to be detonated on a U.S.-bound aircraft.
The bomb, a refined version of the so-called underwear bomb used in a failed attempt on a Detroit-bound flight on Christmas Day 2009, is now at the FBI crime laboratories in Quantico, Virginia.
U.S. officials said they felt confident throughout the operation that the bomb was not an actual threat because the inside source had "control."
White House counter-terrorism advisor John Brennan reiterated on ABC News' "Good Morning America" today that the bomb was not an "active threat," which is why the public was told repeatedly by top administration officials, including Brennan, that there were no known active plots surrounding the anniversary of bin Laden's death.
Brennan would not discuss the status of the would-be bomber, citing operational security, and declined to say whether the insider had himself been tapped to carry out the plot.
"The means that we were able to get this device, we're trying to make sure we protect, again, the equities that are involved with it," he said.
READ: Top Counter-Terrorism Official: No Further Threat From Bomb or Attempted Bomber
Brennan also said he could not say whether there were other bombers still at large.
"You never know what you don't know," Brennan said. "I think people getting on a plane today should feel confident their intelligence services are working day in and day out to stop these IEDs [improvised explosive devices] from getting anywhere near a plane, but also I think when they go through the security measures at airports, they understand why they're in place."
Authorities told ABC News that the device was non-metallic, meaning it could be easy to get through at least one layer of metal-detecting airport security, and had an improved triggering mechanism over the one that failed on Christmas Day in 2009. Department of Homeland Security head Janet Napolitano said today there was a "high likelihood" the device would have been detected had the bomber attempted to slip it through U.S. airport security, but other officials noted that the bomb would've come from an airport abroad, which do not always have the same security standards.
And what Brennan knows and did not say, according to officials, is that several other elements of the plot were under investigation, including possible additional bombers and other kinds of bombs.
READ: More Al Qaeda Bombs Unaccounted For, Officials Say
New Underwear Bomb From Al Qaeda Master Bombmaker
Late Monday federal officials confirmed that the U.S., working with other intelligence agencies, recovered the explosive device presumably meant to attack a U.S.-bound flight that resembles other bombs manufactured by the Yemen-based al Qaeda affiliate al Qaeda in the Arabian Peninsula (AQAP).
The plot appeared timed to coincide with the first anniversary of Osama bin Laden's death, but the bomber did not get as far as purchasing plane tickets or choosing a flight. As ABC News first reported last week, the plot led the U.S. to order scores of air marshals to Europe to protect U.S.-bound aircraft. Flights out of Gatwick Airport in England received 100 percent coverage, according to U.S. officials.
Al Qaeda bombmaker Ibrahim al-Asiri was again the mastermind of the plot, according to U.S. and other intelligence sources. Asiri designed the bombs in the failed printer-bomb cargo plane plot of 2009 and earlier planted a bomb in the rectum of his brother, who died in a suicide attack on the Saudi intelligence chief. He also made Abdulmutallab's underwear bomb, which failed to detonate properly.
The FBI is currently examining the new bomb and is "exploiting" it for intelligence, Brennan said.
But according to former White House counter-terrorism advisor and current ABC News consultant Richard Clarke, the insider's escape from Yemen could put counter-terror operations at a disadvantage from here on out.
"You have to wonder if this plot was foiled by someone on the inside, whether or not that means that source is blown and therefore they no longer have someone on the insde and would not know about the next plot," Clarke said.
U.S. officials said Fahd al-Quso, the head of operations for AQAP, was killed over the weekend by a U.S. drone strike. Asiri, the bombmaker, is still at large, and is believed to be training other bombmakers and making other bombs, all aimed at U.S. aircraft.
AQAP has been described by numerous U.S. officials as a top security threat to the U.S. homeland, more so even than central al Qaeda formerly led by Osama bin Laden.