WASHINGTON â€"    The CIA thwarted an ambitious plot by Al Qaeda's affiliate in Yemen to destroy a U.S.-bound airliner using a bomb with a sophisticated new design around the one-year anniversary of the killing of Usama bin Laden, The Associated Press has learned.

  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 said.

  The FBI is examining the latest bomb to see whether it could have passed through airport security and brought down an airplane, officials said. They said 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 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.

  The operation 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. The AP 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. has never officially acknowledged.

  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.

  The 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. It has set up terrorist camps and, in some areas, even operates as a de facto government.

  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.