The U.S. and allied governments tightened their scrutiny of air cargo and shipped packages Monday as investigators tried to trace bomb parts and scanned for more mail bombs possibly sent from Yemen.
An official United Arab Emirates security source said authorities are tracing the serial numbers of a mobile phone circuit board and computer printer used in a mail bomb sent from Yemen and found in Dubai last week.
As of Monday morning, no fingerprints or DNA have been recovered from the two devices but testing is continuing, a law enforcement source tells CBS News. Officials believe the two bombs were constructed by the same people or person who built the device used in the thwarted Christmas Day plot because there is a similar non-metallic element to the structure of all three bombs.
Meanwhile, Yemeni security officials said that a leading al Qaeda militant in Yemen who surrendered to Saudi Arabia last month that led to the thwarting of the mail bomb plot.
Authorities believe Yemeni-based terrorists sent two mail bombs addressed to Jewish synagogues in Chicago last week, but the devices may have been aimed at blowing up planes in flight. While in the United Arab Emirates and the United Kingdom, U.S. officials warn there may be more in the system.
U.S. officials have said an alert from Saudi Arabia led to the interception on Friday of two explosive devices, hidden in packages addressed to Chicago-area synagogues, on planes transiting in Britain and Dubai. Al Qaeda in the Arabian Peninsula, the terror group's affiliate in Yemen, is suspected in the attempted bombing.
According to CBS News terrorism consultant Juan Zarate, al Qaeda's affiliate group in Yemen is "the most dangerous of al Qaeda's branches or allies."
The Saudi newspaper Al-Watan on Monday cited Saudi security officials saying that the kingdom gave U.S. investigators the tracking numbers of the packages.
The UAE security official told The Associated Press Monday the emirates are sharing the bomb part serial numbers with the United States, Yemen and other countries involved in the probe in an effort to track the bombs' origins.
The person spoke on condition of anonymity because the investigation is ongoing.
In the U.S., counterterrorism officials warned local law enforcement and emergency personnel Monday to be on the watch for mail with unusual characteristics that could mean dangerous substances are hidden inside.
The FBI and Homeland Security Department cautioned that foreign-origin packages without return addresses and excessive postage require a second look, according to an advisory sent to local officials around the country that was obtained Monday by The Associated Press.
John Pistole, the head of the Transportation Security Administration, told CBS' "The Early Show" on Monday that the TSA was working with its partners across the globe to try to identify where any other suspect packages might be.
"We're aware that were facing a determined enemy," Pistole told "Early Show" co-anchor Maggie Rodriguez, adding that TSA agents had been sent to Yemen to help screen U.S.-bound cargo - so when a ban imposed Saturday on all shipments from the Arab country to the U.S. is dropped, packages can be shipped more safely.
Major cargo firms have already suspended shipments from Yemen and on Monday, Germany's aviation authority said the country has extended its ban on cargo aircraft from Yemen to include passenger flights amid the current terrorist threat.
One of the bombs that was mailed from Yemen and found by authorities was routed to London through the UPS hub in Cologne.
German aviation agency spokeswoman Cornelia Cramer said that passenger flights from Yemen were being suspended until further notice. Germany stopped package deliveries from Yemen over the weekend.
The mail bomb plot was narrowly averted, officials said. One device Britain and another seized in Dubai in the United Arab Emirates was unwittingly .
Investigators were still piecing together the potency and construction of two bombs they believed were designed by the working for the Yemen-based faction thought to be behind the plot.
Sources tell CBS News that about 15 other "suspect" packages sent from Yemen around the same time as the bombs have now been located and cleared. But, CBS News correspondent Bob Orr reports, officials have voiced concern that there could still be other explosive packages out there, and either way, AQAP presents a long term threat to the U.S.
Authorities in the UAE discovered the powerful explosive PETN in a shipment that arrived at Dubai airport on a Qatar Airways passenger flight last week. The same explosive is the hallmark of a series of recent terror attempts by al Qaeda in the Arab Peninsula, the militant faction suspected in the mail bomb plot.
U.S. intelligence officials believe the suspected bombmaker is a 28-year-old Saudi named Ibrahim Hassan al-Asiri, thought to be in Yemen. Al-Asiri has been previously tied to a failed bombing attempt last Christmas Day on a Detroit-bound plane and an earlier failed attempt to kill a Saudi counterterrorism official. Both attempts used PETN.
The UAE security source said Monday that a green mobile phone circuit board, but no SIM card, was connected to the HP printer head, which in turn was linked to the explosives. The security source said investigators are examining the circuit board to determine whether it had been used before in the hope it might provide clues to who sent the bomb.
Yemeni authorities hunted suspects linked to AQAP, but released a female computer engineering student arrested Saturday, saying someone else had posed as her in signing the shipping documents.
A Yemeni security official said that security authorities are still hunting for a young woman who is believed to have dropped off the mail bombs at a shipping point in the capital, San'a. An anti-terrorism official told The Associated Press that the young woman acted as a "middleman" with the group.
Authorities acknowledged how close the terrorists came to getting their bombs through, and a senior U.S. official said investigators were still trying to figure out if other devices remained at large.
"We're not presuming that we have, you know, found all (the) devices that are out there," White House counterterrorism adviser John Brennan told Face the Nation host Bob Schieffer on Sunday.
Authorities are also "looking at the potential that they would have been detonated en route to those synagogues aboard the aircraft as well as at the destinations," Brennan told Schieffer.
Watch: Brennan on "Face the Nation"
"Face the Nation" Full Transcript (PDF)
GOP's King: Admin Handled Yemen Plot Perfectly
Brennan headed a meeting of national security and intelligence officials at the White House to determine the U.S. response in concert with a Yemeni government that has been reluctant to give the Americans free rein.
About 50 elite U.S. military experts are in Yemen training its counterterrorism forces and Washington is giving $150 million in military assistance this year for helicopters, planes and other equipment.