The FBI has fingerprint and forensic evidence linking al Qaida's top bomb-maker in Yemen to a trio of explosive devices used in recent attacks on the US, counter-terrorism officials said.
Investigators have pulled a fingerprint of Ibrahim al-Asiri off the bomb which was hidden in the underwear of a Nigerian man accused of trying to blow up a plane over Detroit on Christmas Day 2009.
They also found that the explosives used in that bomb are chemically identical to those hidden inside two printers which were shipped towards Chicago and Philadelphia from Yemen last year.
Osama Bin Laden's death leaves al Qaida's core in Pakistan with a leadership vacuum, one that could make the Yemeni branch known as al Qaida in the Arabian Peninsula even more prominent.
The Yemeni franchise had already eclipsed bin Laden's central organisation to become al Qaida's leading fundraising, propaganda and operational arm.
The FBI has been building cases against a number of high-profile terrorists, including al-Asiri and al-Awlaki. For now, though, there is no guarantee those cases will ever make it to a courtroom.
President Barack Obama has not indicated what he would do if a major terrorist suspect was captured abroad. It is a politically sensitive issue because, even though civilian courts have been used for years to prosecute terrorism cases, Republicans have portrayed Mr Obama as weak on terrorism whenever he discusses that option.
Intelligence officials have long believed that al-Asiri helped build the Christmas and cargo bombs but have never disclosed how they were able to directly link him to the failed attacks.
The fingerprint would help establish al-Asiri's identity if he were ever apprehended, possibly allowing the Justice Department to extradite him to the US for prosecution.
In March, the State Department designated al-Asiri a terrorist and banned Americans from doing business with him. The US said he was also involved in planning to bomb Saudi oil facilities.