Last updated 5:15 a.m. Eastern
Authorities on three continents thwarted multiple terrorist attacks aimed at the United States from Yemen on Friday, seizing two explosive packages addressed to Chicago-area synagogues and packed aboard cargo jets. The plot triggered worldwide fears that al Qaeda was launching a major new terror campaign.
President Barack Obama called the coordinated attacks aand U.S. officials said they were increasingly confident that , the group responsible for the failed Detroit airliner bombing last Christmas, was responsible.
Parts of the plot might remain undetected, Obama's counterterror chief warned. "The United States is not assuming that the attacks were disrupted and is remaining vigilant," John Brennan said at the White House.
According to two CBS News sources, the explosive material discovered Friday was, the same chemical used by failed Christmas Day bomber Umar Farouk Abdulmutallab.
Dubai police said Saturday one of the two seized devices, discovered in a shipment of air cargo from Yemen and bound for the United States, contained the powerful explosive PETN and bore the hallmarks of al Qaeda. They said in a statement carried by official state news agency WAM that the explosives were discovered in the ink cartridge of a computer printer. They say the device, sent from Yemen in a FedEx shipment, was prepared in a "professional manner."
CBS News national Security Correspondent David Martin reports Saudi Arabia tipped off authorities to the threat. Intelligence officials have been monitoring the suspected plot for days, an official said.
An official United Arab Emirates security source said the package discovered there was a device containing explosive materials. This does not mean they were actual bombs, CBS News reports. Some tests were negative but the latest tests are positive for at least some explosives.
It's not yet clear that the devices contained enough material - or the right combination of materials to produce an explosion, reports CBS News justice correspondent Bob Orr. But al Qaeda in the Arabian Peninsula has experienced bomb makers. Previous explosives have been hidden in cassette cases, picture frames and radios. Officials do not know if the devices were designed to explode in the air or needed to be detonated by a person on ground, presumably once they arrived in Chicago.
Both packages were sent from the same address in Yemen to Jewish organizations in Chicago, U.S. officials said.
The package in England, discovered aboard a plane in East Midlands, north of London, contained a printer toner cartridge with wires and powder. It was found during routine screening of cargo in England, prompting authorities to scour three planes and a truck in the United States on Friday, U.S. officials said.
A source told CBS News that the packages in the U.K. and Dubai contained a syringe, powder and cell phone components. (Scroll down to see a photo of one of the cartridges.)
A Joint Terrorism Task Force source told CBS News that investigators were looking for between 10-20 packages shipped out of the UPS office in Sanna, Yemen during the same time frame.
Yemeni officials said they had launched a terrorism investigation, and Scotland Yard said its investigators were testing a number of items seized from the plane in East Midlands.
In the U.S., searches were conducted in Philadelphia, Newark, N.J., and New York City. Local officials said all of the suspicious items and UPS planes that were searched had been given the "all clear."
The White House says Mr. Obama's weekend travel plans to campaign ahead of the midterm elections will not be affected by the terror probe.
UPS said it is immediately suspending shipments out of Yemen after authorities thwarted the potential attack.
"As a precaution, DHS has taken a number of steps to enhance security," the Homeland Security Department said in a statement. "Some of these security measures will be visible while others will not."
Since the failed Christmas bombing of a Detroit-bound airliner, Yemen has been a focus for U.S. counterterrorism officials. Before that attack, the U.S. regarded al Qaeda's branch in Yemen as primarily a threat in the region, not to the United States.
The Yemen branch known as al Qaeda in the Arabian Peninsula has since become a leading source of terrorist propaganda and recruiting. Authorities believe about 300 al Qaeda members or cells operate in Yemen.
The Yemeni government has stepped up counterterrorism operations, with help from the U.S. military and intelligence officials. Mohammed Shayba, general-director of the state airline's cargo department, said the government is conducting an investigation.
"Those in charge are in constant meetings and they are investigating and taking the issue seriously," he told The Associated Press.
Friday afternoon, an Emirates Airlines passenger jet carrying cargo from Yemen was, U.S. officials said. They said it was a precautionary action.