Yemen has freed a woman suspected of mailing two parcel bombs destined for the US, saying she has been a victim of identity theft.
"Authorities concluded that this was a case of stolen identity by an individual who knew the detained suspect's full name, address and telephone number," a Yemeni official said on Sunday.
Hanan al-Samawi, a 22-year-old student, had been detained a day earlier after she was tracked down through a telephone number left with a cargo company.
But when the shipping agent was called in to identify her, he said she was not the right person. Al-Samawi is now on bail, along with her mother who was also detained.
"Thank god she's been released. The problem is over. The truth is revealed," Mohamed al-Samawi, Hanan's father, said.
The packages, found at a UK airport and in a cargo terminal in Dubai on Friday, were addressed to Jewish synagogues in Chicago.
Theresa May, the British home secretary, said the bomb discovered on the plane that landed in the UK was powerful enough to bring down the aircraft.
A US official and a British security consultant said the device, hidden in a printer cartridge, was sophisticated enough that it nearly slipped past UK investigators even after they were tipped off.
The incident has led governments to re-examine airport security systems.
David Cameron, the British prime minister, is expected to chair an emergency committee meeting later on Monday while in Yemen authorities have announced a crackdown on all cargo shipments.
A US official said Ibrahim Hassan al-Asiri, a Saudi bombmaker believed to be working with al-Qaeda in the Arabian Peninsula, is now a key suspect in the plot.
Al-Asiri, who tops a Saudi Arabian terrorism wanted list, is the brother of a suicide bomber killed last year in a bid to assassinate Prince Mohammed bin Nayef, the Saudi counterterrorism chief.
The latest bomb plot, as well as the failed attack on a US-bound airliner on Christmas Day 2009, involved the use of pentaerythritol trinitrate (PETN), a highly potent explosive which is difficult to detect in security screenings.
|Al-Asiri is believed to be hiding in Marib province [AFP]
At least one of the packages sent from Yemen contained PETN.
"The individual who has been making these bombs ... is a very dangerous individual, clearly somebody who has a fair amount of training and experience," John Brennan, the White House counterterrorism adviser, told ABC News.
"We need to find him. We need to bring him to justice as soon as we can."
Brennan also said evidence suggested the same person constructed the Yemen parcel bombs and the device worn by Umar Farouk Abdulmutallab, the Nigerian man who attempted to ignite a bomb in the Christmas Day attack.
Yemeni security officials said they are searching for al-Asiri, who is believed to be in Marib province.
Al-Qaeda's Saudi and Yemeni branches merged in January 2009 to form Al-Qaeda in the Arabian Peninsula under the leadership of Nasser al-Wahishi, a former aide to Osama bin Laden who staged a dramatic jail break from a Yemeni prison with 22 others in 2006.
In the past year, the organisation has emerged as "one of the most dangerous branches of al-Qaeda", according to a US assessment.
The organisation calls for the overthrow of the Saudi and Yemeni governments and has carried out a string of brazen attacks against local security forces.
Although the number of hard core al-Qaeda fighters in Yemen is only believed to number in the low hundreds, they are aided by sympathetic local tribes who see the central government as corrupt and oppressive.
The latest bomb plot has put the security of air cargo in the spotlight. The industry is worth about $100bn globally and the freight company UPS alone is shipping 15 million parcels every day.
Al Jazeera's Dan Nolan, reporting from Dubai, said that only about 15 or 20 per cent of all cargo is ever screened.
"But the biggest concern out of this latest plot is that even if all that cargo is screened, it would appear that none of the technology available is actually capable of picking up this PETN," he said.
"It's going to take some kind of new and very expensive technology to be able to track this stuff down and obviously there is going to be huge ramifications for the cargo industry as to how they are going to put that into place and how quickly they can do it."