Washington:
American intelligence officials in September intercepted several packages containing books, papers, CDs and other household items shipped to Chicago from Yemen and considered the possibility that the parcels might be a test run for a terrorist attack, two officials said Monday night.
Now the intelligence officials believe that the shipments, whose hour-by-hour locations could be tracked by the sender on the shippers' Web sites, 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.
In September, after American counterterrorism agencies received information linking the packages to Al Qaeda in the Arabian Peninsula, the terror network's branch in Yemen, intelligence officers stopped the shipments in transit and searched them, said the officials, who would discuss the operation only on the condition of anonymity.
They found no explosives, and the packages were permitted to continue to what appeared to be "random addresses" with no connection to the terrorist group in Chicago.
American intelligence officials in September intercepted several packages containing books, papers, CDs and other household items shipped to Chicago from Yemen and considered the possibility that the parcels might be a test run for a terrorist attack, two officials said Monday night.
Now the intelligence officials believe that the shipments, whose hour-by-hour locations could be tracked by the sender on the shippers' Web sites, 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.
In September, after American counterterrorism agencies received information linking the packages to Al Qaeda in the Arabian Peninsula, the terror network's branch in Yemen, intelligence officers stopped the shipments in transit and searched them, said the officials, who would discuss the operation only on the condition of anonymity.
They found no explosives, and the packages were permitted to continue to what appeared to be "random addresses" with no connection to the terrorist group in Chicago.
"At the time, people obviously took notice and -- knowing of the terrorist group's interest in aviation -- considered the possibility that AQAP might be exploring the logistics of the cargo system," one of the officials said, referring to Al Qaeda in the Arabian Peninsula.
The apparent test run might have permitted the plotters to estimate when cargo planes carrying the doctored toner cartridges would be over Chicago or another city.
That would conceivably enable them to set timers on the two devices to set off explosions where they would cause the greatest damage.
The September shipments were first reported by ABC News on Monday night, which also noted that Inspire, the English-language magazine of Al Qaeda in the Arabian Peninsula, recently published a picture of the Chicago skyline.
One of the officials said that when the American intelligence agents received a tip from Saudi intelligence officials last week that bombs might be on cargo flights to Chicago from Yemen, analysts "recalled the incident and factored it in to our government's very prompt response."
"Both events reflect solid intelligence work," the official said.
On Monday, Germany, France and Britain said they had banned cargo shipments from Yemen, following a similar move by the United States. Britain prohibited passengers from carrying printer cartridges aboard flights, and Germany halted passenger flights from Yemen as well.
Many countries have stepped up cargo screening, but no additional bombs have been found.
After the recovery of the unexploded printer cartridges in Dubai and Britain on Friday, Yemeni and American intelligence officials have stepped up the hunt for Ibrahim Hassan al-Asiri, 28, a Saudi who is believed to be the top technical expert of Al Qaeda in the Arabian Peninsula.
They believe he designed the underwear explosives that failed to detonate aboard a Detroit-bound airliner last Dec. 25, as well as the body-cavity bomb that killed his younger brother, Abdullah al-Asiri, in a failed attempt last year to assassinate the top Saudi counterterrorism official, Prince Mohammed bin Nayef.
In a related development, a Yemeni official in Washington said late Monday night that prosecutors in Yemen intend to charge the American-born cleric Anwar al-Awlaki later this week with "the crime of promoting violence and the killing of foreigners."
The official, who asked not to be named, said the case would likely be sent to a specialized criminal court in Sana, the capital.
No evidence has been made public linking Mr. Awlaki to the printer cartridge bombs, but intelligence officials believe he played a role in the failed airliner bombing last December, and he has publicly called for more attacks on the United States.
Early this year, he became the first American citizen to be placed on the Central Intelligence Agency's list of terrorists approved for targeted killing.
On Monday, information about the latest failed plot continued to emerge.
An American official said that the addresses on the packages were outdated addresses for Jewish institutions in Chicago.
But in place of the names of the institutions, the packages bore the names of historical figures from the Crusades and the Spanish Inquisition, the official said.
The addresses are one reason that investigators now believe the plan may have been to blow up the planes, since there were no longer synagogues at the Chicago locations.
Explosives experts with the Federal Bureau of Investigation have been sent to London and Dubai to inspect the printer bombs, and technicians planned to "reverse-engineer" the bombs to understand their construction and purpose, Janet Napolitano, the homeland security secretary, told National Public Radio.
The Yemeni president, Ali Abdullah Saleh, said Sunday that he would keep up pressure on Al Qaeda, which he said had killed 70 members of the Yemeni Army and security forces during the past four weeks.
American counterterrorism officials, meanwhile, said they were taking a new look at the crash of a United Parcel Service cargo plane in Dubai on Sept. 3 in light of the explosives plot, which used both U.P.S. and FedEx. An investigation of the crash, which involved an onboard fire and killed the two pilots, found no evidence of an explosion.
New details about the two explosive packages were disclosed by security officials in several countries, who discussed the continuing investigation on condition of anonymity.
The explosive powder, pentaerythritol tetranitrate, or PETN, was found inside toner cartridges that were themselves inside HP LaserJet P2055 printers, according to officials from Germany and the United Arab Emirates.
German security officials also offered new details about the two bombs, one of which was on a plane that made a stop in Cologne.
They said that bomb, which was found at the East Midlands Airport near Nottingham, England, contained 400 grams, or about 14 ounces, of PETN, one of the most powerful explosives known.
The one found in Dubai contained 300 grams of PETN, the officials said.
Neal Langerman, an expert on explosives at Advanced Chemical Safety, a consulting firm in San Diego, said 14 ounces of PETN is the equivalent of five pounds of TNT.
He said that a one-pound stick of TNT would level a house.
Both bombs contained circuit boards from cellphones, but the phone parts appeared to be used as timers, because the so-called SIM cards necessary to receive calls were missing, American officials said.
Their construction appeared to support the conclusion, announced Sunday by John O. Brennan, the White House counterterrorism adviser, that the bombs were designed to blow up aboard the aircraft.
At least one of the packages was initially carried out of Yemen on two Qatar Airways passenger flights, and it was unclear whether they were intended to take down those passenger jets or the U.P.S. and FedEx cargo planes scheduled later to carry them to the United States.
An official familiar with the investigation said that both packages bore the name of a Yemeni student, Hanan al-Samawi, as the sender. Yemeni officials arrested Ms. Samawi but released her after determining that the packages were dropped off at the U.P.S. and FedEx offices in Sana, the Yemeni capital, not by Ms. Samawi but by another woman using her identity.
At the core of the shipping plot, American officials believe, was Mr. Asiri, the suspected Qaeda bomb maker. Saudi news accounts say he is the son of a Saudi military man and grew up in a religious family in the Saudi capital, Riyadh; studied chemistry at King Saud University, and later joined a militant cell hoping to fight the Americans in Iraq.
But he does not appear to have fought in either Iraq or Afghanistan. He appears to have gotten his training after moving to Yemen around 2005.