Authorities intercepted explosives on cargo planes en route from Yemen on Friday after warnings from Saudi Arabian officials. US and UK authorities are investigating the apparent plot to bomb Jewish targets in Chicago.
The US and UK are investigating a terror threat after explosive material was found in packages on two cargo planes headed for the US from Yemen on Friday.
US President Barack Obama vowed to find the culprits behind the attempted terrorist attack.
Speaking to reporters at the White House, Obama called the two parcels addressed to Jewish houses of worship in Chicago a "credible terrorist threat," and said he would spare no effort in investigating their origins.
UK Home Secretary Theresa May confirmed on Saturday that the device intercepted at East Midlands airport and bound for the US was "viable".
"The target may have been an aircraft and had it detonated, the aircraft could have been brought down," she told reporters after a meeting with the UK government's emergency committee Cobra.
One of the packages was found in the UK, the other in Dubai. Both were addressed to Chicago-area synagogues.
Police in Dubai confirmed that one of the parcels contained "a computer printer whose ink contained explosive material" and that the manner in which the device was prepared bore "the hallmarks of those used by terrorist organizations like al Qaeda."
The explosive material was PETN, the same chemical used by the Nigerian man who attempted to blow up a plane over Detroit on Christmas Day in 2009.
Both of the parcels originated in Yemen, the base of al Qaeda in the Arabian Peninsula. The group had previously claimed responsibility for plotting the attempted Christmas bombing.
Obama's top national security advisor John Brennan said all packages originating from Yemen would now be "carefully screened."
The White House said Saudi Arabia provided a tip about the threat from Yemen, while Britain and the United Arab Emirates also supplied information.
One of the packages was discovered on a United Parcel Service (UPS) cargo plane at East Midlands Airport, about 260 kilometers (160 miles) north of London. The other was discovered at a FedEx facility in Dubai.
A spokesman for FedEx said the company has embargoed all shipments originating from Yemen. UPS said it had suspended all cargo flights out of the country.
Brennan added that "dry runs" of terrorist attacks typically do not contain actual explosives, meaning that the incident may have been an actual planned terrorist plot. He stipulated that he did not yet have all the details behind the incidents.
German Defense Minister Karl-Theodor zu Guttenberg warned that terrorist attacks are a constant threat these days.
"For some it seems abstract, but it's quite concrete, " he told Reuters TV on Saturday. "That's why we have to adjust the way we think about security."
Despite Gutternberg's statement, German federal police said Berlin has not stepped up inspections of postal traffic, citing the high level of existing surveillance measures.
Meanwhile, Yemeni officials ramped up security in the capital Sanaa on Saturday, deploying heavily armed police to carry out vehicle searches and identity checks.
Author: Sarah Harman, Andrew Bowen, Nicole Goebel (AP, AFP, Reuters)
Editor: Kyle James