U.S. intelligence officials believe packages intercepted in September with books and other items shipped from Yemen may have been part of last week's plot to send bombs in airline cargo shipments, the New York Times reports.

Such air freight shipments have hour-by-hour tracking, leading to speculation the September packages "may have been used to plan the route and timing for two printer cartridges packed with explosives that were sent from Yemen and intercepted in Britain and Dubai on Friday," the newspaper reports.

Officials learned about the packages and searched them in September, allowing their delivery after finding no explosives or terrorist connections. The package bombs discovered last week were intercepted after a tip from Saudi intelligence officials.

When they learned of the packages being shipped on airplanes, U.S. intelligence officials remembered the September shipment, which now is viewed as a test run. "Both events reflect solid intelligence work," an unnamed intelligence official told the Times.

Yemen reportedly has stepped up efforts to find Ibrahim al-Asiri, who is considered by law enforcement and intelligence officials to be the main bomb maker for al-Qaida in the Arabian Peninsula and the mastermind of the recent plot. On Monday, the Investigative Project on Terrorism unearthed video of Asiri saying farewell to his brother last year before sending him on a suicide mission targeting the Saudi prince in charge of counter terrorism.