In September, U.S. authorities seized three boxes after receiving intelligence linking the packages to Al Qaeda in the Arabian Peninsula. During an investigation, officials found papers, books and other materials, but no evidence of explosives. They eventually permitted the packages to continue to what appeared to be "random addresses" in Chicago, according to the New York Times.
"We received information several weeks ago that potentially connected these packages to AQAP. The boxes were stopped in transit and searched," said an official who was familiar with details of the shipments.
The New York Times reports September's suspected dry run could have created a timetable for an actual attack. By tracking the packages, plotters could have estimated when the cargo planes flew over Chicago or another city, which would have enabled them to set timers on explosive devices.
The mail bombs recovered Friday in Dubia and Britian contained wired denators that used cell phone techonlogy, according to an official close to the invesitgation.
American Intelligence officials believe 28-year-old Ibrahim Hassan al-Asiri is the suspected bomb-maker. Yemeni and American intelligence officials stepped up the hunt to find him.