A team of FBI experts are examining a sophisticated new Al Qaeda bomb to figure out whether it could have slipped past airport security and taken down a commercial airplane, U.S. officials said.

The bomb was confiscated after the CIA unraveled a terror plot by Al Qaeda in the Arabian Peninsula to destroy a U.S.-bound airliner using an underwear bomb around the one-year anniversary of the killing of Usama bin Laden.

The plot involved an upgrade of the underwear bomb that failed to detonate aboard a jetliner over Detroit on Christmas 2009. This new bomb was also designed to be used in a passenger's underwear, but this time Al Qaeda developed a more refined detonation system, U.S. officials told the Associated Press.

“Initial exploitation indicates that the device is very similar to IEDs that have been used previously by Al Qaeda in the Arabian Peninsula in attempted terrorist attacks, including against aircraft and for targeted assassinations,” the FBI said in a written statement. “The FBI currently has possession of the IED and is conducting technical and forensics analysis on it.”

Officials say the device did not contain metal, meaning it probably could have passed through an airport metal detector. However, it was not clear whether new body scanners used in many airports would have detected it.

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The would-be suicide bomber, based in Yemen, had not yet picked a target or bought his plane tickets when the CIA stepped in and seized the bomb, officials said. It's not immediately clear what happened to the alleged bomber.

A U.S. official told Fox News that Al Qaeda in the Arabian Peninsula, or AQAP, remains "committed to striking targets in Yemen, Saudi Arabia, the Homeland, and Europe. And AQAP is probably feeling pressure to conduct a successful attack to, from their perspective, avenge the deaths of bin Laden and Awlaki.”

A team of U.S Navy SEALs killed bin Laden during a raid last May on his compound in Pakistan. Anwar al-Awlaki, an American-born cleric hiding in Yemen, was killed by a U.S. drone strike in September.

Al-Awlaki was closely tied to AQAP and was the inspiration for multiple attacks on American targets, including the failed Christmas Day underwear bomb attack in 2009.

“It is our assessment that the threat from AQAP is growing due to the territorial gains the group made during the political standoff in Yemen that lasted from early 2011 until this past February," the U.S. official told Fox News. "Those territorial gains have allowed the group to establish additional training camps.”

In a press conference at the Pentagon with China's Minister of National Defense, Gen. Liang Guanglie, Defense Secretary Leon Panetta said the US has to "continue to remain vigilant against those who would seek to attack this country and we will do everything necessary to keep America safe."

The operation to thwart the latest bomb plot unfolded even as the White House and Department of Homeland Security assured the American public that they knew of no Al Qaeda plots against the U.S. around the anniversary of bin Laden's death.

"We have no credible information that terrorist organizations, including Al Qaeda, are plotting attacks in the U.S. to coincide with the anniversary of bin Laden's death," White House Press Secretary Jay Carney said on April 26.

But Obama was being briefed on the plot in April by counterterrorism adviser John Brennan, Deputy NSC Spokesperson Caitlin Hayden said.

“While the president was assured that the device did not pose a threat to the public, he directed the Department of Homeland Security and law enforcement and intelligence agencies to take whatever steps necessary to guard against this type of attack,” she said.

Sen. Dianne Feinstein, D-Calif., the Senate Intelligence Committee Chairwoman, told Fox News she was informed of the plot a half hour before it went public.

House Homeland Security Committee Chairman Pete King, R-N.Y., said lawmakers are only aware of certain threat streams, but he did not know about this one.

"Some things are very closely held. I understand why," he told Fox News. "You're not going to hear me complain about it."

The AP said it learned about the thwarted plot last week but agreed to White House and CIA requests not to publish it immediately because the sensitive intelligence operation was still under way. Once officials said those concerns were allayed, the AP decided to disclose the plot Monday despite requests from the Obama administration to wait for an official announcement Tuesday.

U.S. officials, who were briefed on the operation, insisted on anonymity to discuss the case, which the U.S. hadn't officially acknowledged until now.

It's not clear who built the bomb, but, because of its sophistication and its similarity to the Christmas bomb, authorities suspected it was the work of master bomb maker Ibrahim Hassan al-Asiri. Al-Asiri constructed the first underwear bomb and two others that Al Qaeda built into printer cartridges and shipped to the U.S. on cargo planes in 2010.

Both of those bombs used a powerful industrial explosive. Both were nearly successful.

A government source also told Fox News that a second threat stream, that involved surgically-implanted body bombs, was being monitored out of the Middle East.

The latest operation is an intelligence victory for the United States and a reminder of Al Qaeda's ambitions, despite the death of bin Laden and other senior leaders. Because of instability in the Yemeni government, the terrorist group's branch there has gained territory and strength.

But along with the gains there also have been losses. The group has suffered significant setbacks as the CIA and the U.S. military focus more on Yemen. On Sunday, Fahd al-Quso, a senior Al Qaeda leader, was hit by a missile as he stepped out of his vehicle along with another operative in the southern Shabwa province of Yemen.

Al-Quso, 37, was on the FBI's most wanted list, with a $5 million reward for information leading to his capture. He was indicted in the U.S. for his role in the 2000 bombing of the USS Cole in the harbor of Aden, Yemen, in which 17 American sailors were killed and 39 injured.

Al-Quso was believed to have replaced Anwar al-Awlaki as the group's head of external operations. Al-Awlaki was killed in a U.S. airstrike last year.

Fox News' Catherine Herridge, Chad Pergram, John Brandt and the Associated Press contributed to this report.