WASHINGTON (AP) — U.S. bomb experts are picking apart a sophisticated new al-Qaida improvised explosive device, a top Obama administration counterterrorism official said Tuesday, to determine if it could have slipped past airport security and taken down a commercial airplane.

Officials told The Associated Press a day earlier that discovery of the unexploded bomb represented an intelligence prize resulting from a covert CIA operation in Yemen, saying that the intercept thwarted a suicide mission around the anniversary of the killing of Osama bin Laden.

The device did not contain metal, meaning it probably could have passed through an airport metal detector. But it was not clear whether new body scanners used in many airports would have detected it. The device is an upgrade of the underwear bomb that failed to detonate aboard a jetliner over Detroit on Christmas 2009. Officials said this new bomb was also designed to be used in a passenger's underwear, but this time al-Qaida developed a more refined detonation system.

John Brennan, President Barack Obama's counterterrorism adviser, said Tuesday the discovery shows al-Qaida remains a threat to U.S. security a year after bin Laden's assassination. And he attributed the breakthrough to "very close cooperation with our international partners."

"We're continuing to investigate who might have been associated with the construction of it as well as plans to carry out an attack," Brennan said. "And so we're confident that this device and any individual that might have been designed to use it are no longer a threat to the American people."

On the question of whether the device could have been gone undetected through airport security, Brennan said, "It was a threat from a standpoint of the design." He also said there was no intelligence indicating it was going to be used in an attack to coincide with the May 2 anniversary of bin Laden's death.

Rep. Peter King, R-N.Y., chairman of the House Homeland Security Committee, said Tuesday that "a number of countries" provided information and cooperation that helped foil the plot. He said he had no information on the would-be bomber, but that White House officials had told him "He is no longer of concern," meaning no longer any threat to the U.S.

Sen. Dianne Feinstein, D-Calif., who heads the Senate Intelligence Committee, told reporters Monday night that she had been briefed Monday about an "undetectable" device that was "going to be on a U.S.-bound airliner."

There were no immediate plans to change security procedures at U.S. airports.

U.S. officials declined to say where the CIA seized the bomb. The would-be suicide bomber, based in Yemen, had not yet picked a target or purchased plane tickets when the CIA seized the bomb, officials said. It was not immediately clear what happened to the would-be bomber.

President Barack Obama had been monitoring the operation since last month, the White House said Monday evening. White House spokeswoman Caitlin Hayden said the president was assured the device posed no threat to the public.

"The president thanks all intelligence and counterterrorism professionals involved for their outstanding work and for serving with the extraordinary skill and commitment that their enormous responsibilities demand," Hayden said.

Secretary of State Hillary Rodham Clinton said: "The device did not appear to pose a threat to the public air service, but the plot itself indicates that these terrorist keep trying to devise more and more perverse and terrible ways to kill innocent people. And it a reminder of how we have to keep vigilant." Clinton spoke during a news conference Tuesday in New Delhi with Indian External Affairs Minister S.M. Krishna.

The operation unfolded even as the White House and Homeland Security Department assured the public that they knew of no al-Qaida plots against the U.S. around the anniversary of bin Laden's death.

On May 1, the Homeland Security Department said, "We have no indication of any specific, credible threats or plots against the U.S. tied to the one-year anniversary of bin Laden's death."

The AP learned about the thwarted plot last week but agreed to White House and CIA requests not to publish a story 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.

The FBI and Homeland Security acknowledged the existence of the bomb late Monday. Other officials, who were briefed on the operation, insisted on anonymity to discuss details of the plot, many of which the U.S. has not officially acknowledged.

It's not clear who built the bomb, but because of its sophistication and its similarity to the Christmas Day 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-Qaida 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.

The new underwear bomb operation is a reminder of al-Qaida'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. It has set up terrorist camps and, in some areas, even operates as a de facto government.

On Monday, al-Qaida militants staged a surprise attack on a Yemeni army base in the south, killing 22 soldiers and capturing at least 25. The militants managed to reach the base both from the sea and by land, gunning down troops and making away with weapons and other military hardware after the blitz, Yemeni military officials said.

But the group has also suffered significant setbacks as the CIA and the U.S. military focus more on Yemen. On Sunday, Fahd al-Quso, a senior al-Qaida 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.

The new Yemeni president, Abed Rabbo Mansour Hadi, has promised improved cooperation with the U.S. to combat the militants. On Saturday, he said the fight against al-Qaida was in its early stages. Hadi took over in February from longtime authoritarian leader Ali Abdullah Saleh.

Brennan appeared on ABC's "Good Morning America," the "CBS This Morning" show and NBC's "Today" show. King was interviewed on CNN.

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Associated Press writers Kimberly Dozier, Eileen Sullivan and Alan Fram in Washington and Matthew Lee in New Delhi contributed to this report.

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Contact the Washington investigative team at DCinvestigations(at)ap.org

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