(The package of explosives was initially sent to his office at Penn State before being forwarded to Vanderbilt).
The possible existence of a fifth attempted bomber has previously been a matter of debate among investigators pondering the significance of an abandoned package of explosives similar to those that failed to detonate on July 21.
A railroad patrolman found the package of explosives buried beneath the tracks near the town of Mocejón, about 30 miles south of Madrid, the interior minister, Ángel Acebes, said at a news conference.
It will also provide a damage assessment from a World Trade Center-style attack with an aircraft or bombs, from a small package of explosives the size of a cake box to an enormous truck bomb that could maim thousands in a crowded place.
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Investigators found an automatic weapon, a machine gun, five packages of plastic explosives and two detonators, according to the report, citing officials involved in the investigation.
Security consultants also have offered various precautions: X-raying packages for explosives; creating "safe rooms" for packages suspected of containing biological agents; having mail room employees contact senders to confirm a package was sent; and setting up procedures to contact the FBI or local law enforcement if a package or letter appears suspicious.
Since the attack on the American Consulate in June, which killed 14 Pakistanis, e-mail messages sent to a Pakistani newspaper and signed Asif Ramzi said 35 packages holding five ounces of explosives each was sent from three post offices.
The searches consist of swabbing bags and packages for explosive residue, and X-raying or opening any packages which turned up positive.
Last Wednesday, CNN anchors were reporting about a series of packages containing explosives that were mailed to Hillary Clinton, Barack Obama, and George Soros, when they were forced evacuate on air because a fire alarm had gone off.
