Security forces in Yemen have arrested a female medical student suspected of posting parcel bombs found on two cargo jets in Dubai and the UK.
She was held at a house in the capital, Sanaa, after being traced through a phone number left with a cargo company.
Her mother was also detained.
UK Prime Minister David Cameron said the device found in Britain could have been designed to detonate in flight.
Two packages were found on US-bound cargo planes in England and Dubai on Friday, addressed to Jewish synagogues in Chicago.
Britain, the United States, France and Germany have now suspended air freight from Yemen.
US Homeland Security Secretary Janet Napolitano says enhanced protections are in place for cargo and security at airlines and airports in response to the discovery of the packages.
She says the increased security measures will vary from airport to airport to ensure there is a level of unpredictability.
Ms Napolitano says the parcel bombs have the hallmarks of al Qaeda, or its affiliate al Qaeda, in the Arabian Peninsula.
British interior minister Theresa May said on Saturday that the package could have brought down an aircraft if it had exploded en route.
The device was taken off a cargo plane at East Midlands airport north of London. A government statement said it arrived from Yemen via Cologne, Germany.
Police in Dubai have also confirmed that the second device also contained explosive.
Ms Napolitano told CNN that it appeared the parcels contained the same type of explosives used in a bombing attempt on an American airliner flying from Amsterdam to Detroit on Christmas Day, which was claimed by AQAP.
Police said the parcel contained explosive pentaerythritol trinitrate in a printer and cartridge. PETN was the material used in the Christmas Day plot, when passengers prevented a bomber from igniting explosives in his underwear.
Ms Napolitano said checks are being made to see if other packages preceded the two that were intercepted.