Yemen has arrested a female student suspected of mailing explosive parcels from the country to the US.
The arrest took place on Saturday in the capital, Sanaa, after security forces surrounded a house where the suspect was hiding.
"Yemeni security forces arrested a woman suspected of sending two parcel bombs," Yemen's defence ministry said.
The woman's lawyer said she was a "quiet student" with no known links to religious or political groups. Her mother was also detained, but was not a prime suspect, the lawyer said.
A Yemeni security official said the woman, an engineering student in her 20s, had been traced through a telephone number she left with a cargo company.
Security officials have been on high alert since the UK and the United Arab Emirates on Friday intercepted two packages containing explosive material that were being shipped by air from Yemen, destined for synagogues in Chicago.
Ali Abdullah Saleh, the Yemeni president, said security services "received information that a girl has sent the parcels from the two cargo companies," apparently referring to UPS and FedEx, the US firms
through which the parcels were sent.
The packages were discovered on Friday at East Midlands Airport, in Nottingham, north of London, and at a courier facility in Dubai.
Qatar Airways confirmed that the parcel bomb discovered in Dubai was carried by two of its passenger planes through Doha.
The airline also stated that "the explosives discovered were of a sophisticated nature whereby they could not be detected by X-ray screening or trained sniffer dogs," and were only discovered after an intelligence tip off.
But Qatar Airways' chief executive, Akbar Al Baker, said the airline's security is as tight as it possibly can be.
"Quite frankly, I don't know what more improvement we can do when there are explosives in the hands of terrorists that cannot be detected by sniffer dogs [or] any available technology today," he said.
"We are doing our best.
"These packages should have been inspected by the courier company; they should have been inspected by the government from where this package was loaded on the airplane.
"It is not the job of the airlines to inspect baggage, it is entirely the job of regulators and governments."
Yemeni authorities seized and examined up to 26 suspect parcels on Saturday. They are also engaged in a hunt for al-Qaeda fighters in Yemen, where Anwar al-Awlaki, a US-born Muslim religious leader, is named as being linked to the plot.
The failed plot has prompted scrutiny of airport security in the UK, where Theresa May, the home secretary, announced a ban on all unaccompanied cargo coming from Yemen into the country.
Security has also increased in the US, where the postal service has temporarily stopped accepting inbound mail originating in Yemen.
Germany has also banned air freight from Yemen from entering the country.
Al Jazeera's Monica Villamizar, reporting from Washington, DC, said that US authorities now consider Yemen and Al-Qaeda in the Arabian Peninsula (AQAP) to be "more of a threat to the US and its interests now than even Afghanistan and Pakistan".
She also said that US investigators will now look at previously shipped packages from Yemen to determine if they were used as a "dry run" by al-Qaeda.
'Hallmarks of al-Qaeda'
Police in Dubai said the package they found bore the hallmarks of al-Qaeda. They also said that the ink cartridge it contained was packed with pentaerythritol tetranitrate, or PETN.
"Because it's a plastic explosive it's not going to show up on any X-ray and sniffer dogs, it seems, are also unable to detect it because it's odourless"
Dan Nolan, Al Jazeera correspondent
PETN is the same substance that was packed into the underwear of Umar Farouk Abdulmutallab, the Nigerian man who attempted to ignite a bomb on board an airliner over the US on December 25 last year.
The police said the explosive materials found in Dubai were wired to a mobile phone SIM card hidden inside a printer.
Al Jazeera's Dan Nolan, reporting from Dubai, said PETN is very difficult to detect in airport security screenings.
"It seems to be virtually undetectable," he said.
"Even a UK explosives expert was quoted yesterday as saying that even the most sophisticated explosive detection machines ... struggle to detect PETN. Because it's a plastic explosive it's not going to show up on any X-ray and sniffer dogs, it seems, are also unable to detect it because it's odourless."
Bob Ayers, an independent security analyst, told Al Jazeera that cargo is subject to less stringent security screening than passenger luggage.
The screening of cargo has been a point of debate in the US. In 2007, congress directed the Transportation Security Administration to screen all cargo carried on passenger flights beginning this year, according to US media.
"Cargo is in big pallets, it's wrapped, its prepared for shipment," Ayers said. "You can't X-ray the large pallet in many cases. You don't tear it apart because its already been pre-packaged, so cargo has always been less rigorously inspected than baggage going into a passenger aircraft."
Both UPS and FedEx said they had halted all packages being sent from Yemen to the US while the incident is investigated.
In September, a large fire broke out in the cargo hold of a UPS cargo jet shortly after it took off from the Dubai airport. The plane crashed, killing both crew members. The UAE's general civil aviation authority issued a statement on Sunday saying the possibility of an explosion on board that plane was unlikely.
Source: Al Jazeera and agencies