As officials worldwide scramble to plug security holes exposed by the mail bomb plot uncovered Friday, emerging details show some of the well-hidden explosives travelled on two passenger jets before a tip lead to their discovery.

In an announcement Sunday, a spokesperson for Qatar Airways said one of the two bombs destined for Chicago-area synagogues was transported on two separate passenger aircraft before it was discovered in Dubai.

The spokesperson, who provided the information on condition of anonymity, said the package, which had explosives hidden in a printer cartridge, arrived in Doha, Qatar aboard a Qatar Airways flight from Sana'a, Yemen.

The package was then put on another Qatar Airways plane to Dubai, where authorities discovered it early Friday on a tip from officials in Saudi Arabia.

The second package was found Friday at an airport in England, but only the Saudi tip encouraged security officials to do a second sweep.

On Saturday, authorities suggested that as many as two dozen other packages are being investigated in connection with the plot, which U.S. officials said bears the hallmarks of al Qaeda's subsidiary in Yemen.

John Brennan, counterterrorism advisor to U.S. President Barack Obama, said Sunday officials "have to presume" there might be more package bombs headed for U.S. or international targets.

British Home Secretary Theresa May said the bomb found in England was powerful enough to take down the plane. Security officials actually missed the bomb during their first sweep of cargo at the East Midlands airport and had taken down their security cordon when they were told by Dubai officials about the bomb hidden in the printer cartridge, said British aviation consultant Chris Yates.

"As a direct consequence, they put the cordon back up again and looked again and found the explosives," said Yates, who was speaking on a report from an eyewitness.

Authorities said it is still unclear whether the bombs, which were connected to cellular phones, timers and power supplies, could have gone off while the planes were in the air or once they arrived at their U.S. targets.

The plot has exposed gaps in air cargo security despite tightened regulations brought in after the Sept. 11, 2001 terrorist attacks on the United States.

Six inspectors from the U.S. Transportation Security Administration were scheduled to travel to Yemen Sunday to inspect and identify problems with cargo security practices. They will also recommend improvements to security systems, and to training protocols.

"We're trying to get a better handle on what else may be out there," Brennan told NBC's Meet the Press in one of a series of interviews on the Sunday morning political talk show. "We're trying to understand better what we may be facing."

Brennan told CNN's State of the Union that "we feel good" about the steps taken so far in the wake of the new threat. But "I think we have to presume there might be" additional bombs, he said.

In the wake of the new threat, FedEx and UPS suspended air freight from Yemen.

Suspect released as probe shifts

On Saturday, officials in Yemen arrested a female engineering student who is suspected of mailing the two bombs.

Yemeni authorities have since released her, however, saying the person who signed the shipping documents was posing as the 22-year-old woman.

Officials in Yemen were still searching Sunday for additional suspects who may be carrying forged identification and other documents. A member of Yemen's anti-terrorism unit said the other suspects have known ties to al Qaeda.

Authorities now say forensic analysis of the explosive devices point to the same bombmaker behind devices used in the failed bombing of a Detroit-bound airliner last Christmas and the attack on Saudi Arabia's counterterrorism chief last year.

U.S. intelligence officials believe the suspected bombmaker is a 28-year-old Saudi named Ibrahim Hassan al-Asiri. He is believed to be in Yemen's Marib province.

Together with a U.S.-born preacher Anwar al-Awlaki, Yemeni militants, and former Saudi inmates of Guantanamo, al-Asiri comprises the leadership of Al Qaeda in the Arabian Peninsula.

The terror network's operations in Yemen have been a growing concern for U.S. officials, particularly after the organization was found to be behind the failed U.S. jetliner bombing last Christmas.

The bombs used in that plot, and this most recent one contained the industrial explosive PETN, or pentaerythritol tetranitrate, which was also used by convicted shoe bomber Richard Reid when he tried to destroy a trans-Atlantic flight in 2001.

"They are a dangerous group," Brennan said of the Yemeni cell. "They are a determined group. They are still at war with us and we are very much at war with them. They are going to try to identify vulnerabilities that might exist in the system."

With files from CTV's Joy Malbon in Washington and The Associated Press