One of the parcel bombs bound for the United States was carried on a passenger plane, it’s emerged.
Qatar Airways has revealed that one of two devices sent from Yemen last week was transported on two of its flights before being seized in Dubai.
It had been thought that both bombs had been transported by cargo planes.
Yemen, meanwhile, has freed a woman held on suspicion of involvement in the plot after her arrest sparked protests by her fellow students at Sanaa University.
Authorities are said to have accepted she was impersonated by someone else.
It is now known that the bomb, planted inside a printer ink cartridge container, was filled with an industrial explosive called PETN – the same material used by the suspected bombmaker behind the foiled attempt to bring down a US airliner last Christmas.
US authorities say Isbrahim Hassan al-Asiri is now the prime suspect in the mail bomb plot against synagogues in Chicago.
Governments, airlines and aviation authorities around the world are now reviewing security measures.