(AP) - One of two powerful bombs mailed from Yemen to Chicago-area synagogues traveled on two passenger planes within the Middle East, a Qatar Airways spokesman said Sunday. The U.S. said the plot bears the hallmarks of al-Qaida's offshoot in Yemen and vowed to destroy the group.

The airline spokesman said a package containing explosives hidden in a printer cartridge arrived in Qatar Airways' hub in Doha, Qatar on one of the carrier's flights from the Yemeni capital San'a. It was then shipped on a separate Qatar Airways plane to Dubai in the United Arab Emirates, where it was discovered by authorities late Thursday or early Friday. A second, similar package turned up in England on Friday.

The airline spokesman disclosed the information on condition of anonymity in line with the company's standing policies on conversations with the media. He did not give any timeframe for the two flights in question - the airline operates daily passenger flights from Yemen that could also carry courier packages.

The plot was the latest to expose persistent security gaps in international air travel and cargo shipping nearly a decade after the Sept. 11, 2001 attacks and showed terrorists appear to be probing those vulnerabilities.

In Washington, President Barack Obama's deputy national security adviser John Brennan said authorities "have to presume" there might be more potential mail bombs like the ones pulled from planes in England and the United Arab Emirates.

U.S. inspectors were heading to Yemen to monitor cargo security practices and pinpoint holes in the system. An internal government report, obtained by The Associated Press, said the team of six inspectors from the Transportation Security Administration will give Yemeni officials recommendations and training to improve cargo security. The report also says the agency is considering extending its security directive to increase inspection of cargo for all flights through Nov. 8.

"We're trying to get a better handle on what else may be out there," Brennan told NBC's "Meet the Press" as he made the rounds of the Sunday talk shows representing the Obama administration in the wake of the latest terrorist scare. "We're trying to understand better what we may be facing."