WASHINGTON // The United States intercepted parcels from Yemen in September thought to be a dry run for the package bomb plot, a US official said, as western governments tightened freight and passenger security.
Two parcels addressed to Jewish institutions in Chicago and containing the lethal explosive PETN hidden in ink toner cartridges were uncovered on Thursday in Britain and Dubai on cargo planes en route to the United States.
But now it has emerged that US agents first found suspicious packages from Yemen back in September and linked them "several weeks ago" to al Qa'eda in the Arabian Peninsula, according to a US official.
"The boxes were stopped in transit and searched," the official said late on Monday, confirming that the packages contained no explosives.
"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," the official added.
"When we learned of last week's serious threat, people recalled the incident and factored it in to our government's very prompt response."
ABC News, which broke the news of the test run, said it had been told by senior officials that ever since the September discovery US intelligence agencies had specific concerns about AQAP's interest in Chicago.
The dry run contained household goods including books, religious literature, and a computer disk and were shipped by "someone with ties to al Qa'eda in the Arabian Peninsula," a US official told broadcaster ABC.
Using shipping services UPS and FedEx, the senders could track their test package on the companies' websites, which may have helped them plan the routing and the timing for the bombs they dispatched to the United States.
Meanwhile, western governments imposed new restrictions on freight in the wake of the plot, as Yemen scrambled to contain the fallout by announcing exceptional security measures on all freight leaving Yemeni airports.
A team of US experts is heading to Yemen to provide screening, training and equipment to examine cargo shipments at the main international airport in the capital Sana'a.
Qatar Airways has revealed that one of the packages had been flown from Sana'a to Doha and then on to Dubai on one of its passenger aircraft, heightening concern in Western capitals.
Britain announced Monday it was suspending all unaccompanied air cargo from war-torn Somalia, extending an earlier ban on freight from Yemen.
British Prime Minister David Cameron vowed to work with partners in the Middle East to "cut out the terrorist cancer that lurks in the Arabian Peninsula".
"The fact that the device was being carried from Yemen to the UAE to Germany to Britain en route to America shows the interest of the whole world in coming together to deal with this," Cameron told parliament.
Germany went further, banning all flights from Yemen after the discovery of the bomb at East Midlands airport in Britain, which passed through the German city of Cologne.
The move surprised Yemen, which said it needed help, not punishment.
Its partners should help it "reinforce its efforts to beat terrorism instead of resorting to decisions which can only be likened to collective punishment," a government spokesman said on Tuesday.
The Dubai bomb was composed of a highly explosive combination of PETN and lead azide, hidden inside a computer printer with a circuit board and mobile phone SIM card attached, security officials said.
British Home Secretary Theresa May announced a ban on passengers carrying toner cartridges larger than 500 grams in their hand luggage.
The BBC reported that the bombs had been discovered following a tip-off from a former al Qa'eda militant who handed himself in to Yemeni authorities two weeks ago.
Jabr al-Faifi is a former Guantanamo detainee who was returned to Saudi Arabia for rehabilitation in 2006 but later escaped to Yemen and rejoined al Qa'eda.
An alleged Saudi bombmaker, Ibrahim Hassan al Asiri, has emerged as a key suspect in the bomb plot.
"Al-Asiri's past activities and explosives' experience make him a leading suspect," a US counter-terrorism official said.
The militant, thought to be hiding in Yemen, was already wanted for designing the "underwear" bomb worn by the young Nigerian accused of trying to blow up a US airliner last Christmas.
Months earlier, Asiri sent his brother on a suicide mission, with 100 grams of PETN under his white Saudi robe, to kill the Saudi intelligence chief, who was wounded but survived.