US authorities have said that they knew of al-Qaeda's plans to use international cargo systems several weeks before last week's foiled parcel bomb plot, Al Jazeera has learned.
The authorities are reported to have intercepted packages shipped by the group in September.
"Several weeks ago, we identified packages in transit that appeared to have a connection to al-Qaeda," a US official told Al Jazeera on Tuesday.
"We looked at them very closely, and determined they did not contain explosives. We obviously took this earlier event into account in dealing with last week's cargo threat."
The parcel bombs, addressed to synagogues in Chicago, were discovered at a UK airport and in a cargo terminal in Dubai on Friday.
Qatar Airways said the Dubai parcel had been transported on two of its passenger planes from Sanaa via Doha.
Theresa May, Britain's interior minister, said the package intercepted in the UK was powerful enough to bring down the aircraft, while other officials said the device was so sophisticated that it nearly slipped past investigators despite a tip-off.
The parcel, which was hidden inside a computer printer with a circuit board and mobile phone SIM card attached, was said to contain pentaerythritol trinitrate (PETN), a highly potent explosive, which is difficult to detect in security screenings.
Al Jazeera's Rob Reynolds, reporting from Los Angeles, said that this recent development makes things a lot more interesting but also a lot more murky.
"It is not clear still whether the bombs were intended to reach the destinations in the US, or whether they were designed to bring down the planes in flight," Reynolds said.
"What is certain is that the al-Qaeda group in that region seems to be determined to use this route to further their objectives, much like the incident with the shoe-bomb attempt."
A leading al-Qaeda fighter in Yemen who surrendered to Saudi Arabia last month provided the tip that led to the thwarting of the mail bomb plot, according to Yemeni security officials, The Associated Press (AP) news agency reported on Monday.
The officials said Jabir al-Fayfi, a Saudi who had joined al-Qaeda in Yemen, had told Saudi officials about the plan.
The Yemeni officials spoke on condition of anonymity because they were not authorised to talk to the press.
Several tribal leaders with knowledge of the situation, who similarly spoke on condition of anonymity, confirmed al-Fayfi's role, AP said.
The Saudi newspaper Al-Watan on Monday cited Saudi security officials saying that the kingdom gave US investigators the tracking numbers of the packages.
"The latest announcement about al-Faifi brings to the fore two major issues," Al Jazeera's Hashem Ahelbarra, reporting from Sanaa, said.
"One, that Saudi Arabia enjoys unlimited influence and leverage in Yemen. Number two, is it shows that Saudi managed to infiltrate Al-Qaeda in the Arabian Peninsula.
Ahelbarra said that this was something unheard of in the history of al-Qaeda.
"Usually, when they plan an attack, it is only a small circle of al-Qaeda that is familiar with all the details of the operation," he said.
"The Yemenis don't seem to be happy with the revelations that Saudi was the key player in tipping off the Americans".
Following this incident, a number of countries announced changed security procedures or have placed bans on cargo from Yemen.
Britain banned unaccompanied cargo freight to the UK from Yemen and Somalia, while Germany extended its ban on cargo aircraft from Yemen to include passenger flights.
The Netherlands and Canada suspended all cargo flights from Yemen, while France and the US banned air freight from Yemen in response to the plot.
Source: Al Jazeera and agencies