A tip-off that was crucial to the discovery of two bomb plots targeting Europe came from a former Al-Qaeda militant who handed himself in to Yemeni authorities two weeks ago, the BBC reports.
Jabr al-Faifi is a former Guantanamo detainee who was returned to Saudi Arabia for rehabilitation in 2006 but later escaped to Yemen and rejoined Al-Qaeda.
An alleged Saudi bombmaker, Ibrahim Hassan al-Asiri, has emerged as a key suspect in the bomb plot.
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"Al-Asiri's past activities and explosives' experience make him a leading suspect," a US official said on condition of anonymity.
The militant, thought to be hiding in Yemen, is wanted for a string of high-profile attacks linked to Al-Qaeda.
In August 2009, Asiri sent his 23-year-old younger brother on a suicide mission, with 100 grammes (four ounces) of PETN under his white Saudi robe, to kill Saudi intelligence chief Prince Mohammed bin Nayef, who was wounded but survived.
US officials have said the parcel bombs intercepted in Dubai and Britain were addressed to synagogues in Chicago.
The Wall Street Journal reported that President Barack Obama's administration was considering placing under Central Intelligence Agency authority elite "hunter-killer" special operations teams that operate secretly in Yemen to track and kill Al-Qaeda leaders.
The Pentagon, however, strongly denied the report.
"There is nobody in a leadership position in the Defence Department who's given any serious consideration to the proposal outlined in that article," spokesman Bryan Whitman told reporters.
Washington has stepped up its military assistance to Yemen over the past year and US officials have acknowledged covert operations in the country in the past, although the State Department insists the lead role in fighting the jihadists rests firmly with the Yemeni security forces.
