U.S. intelligence officials said Monday they had intercepted a September “dry run” of the cargo plane bomb plot discovered Friday. According to several people close to the investigation, the September shipment contained no explosives, but rather a carton of household goods including books, religious literature, and a computer disk that were sent to an address in Chicago by someone with ties to al Qaeda in the Arabian Peninsula. After the shipment was discovered, officials were alerted to al Qaeda’s threat, but no one had a specific time or date that an attack would occur. The White House said they only learned of the actual plot Thursday night after a tip from Saudi intelligence. U.S. and British authorities said the bombs, which were hidden in desktop printers, were designed to detonate on board the aircraft carrying them.