Investigators examining explosives found in packages intercepted in Britain and Dubai suspect the material, preliminarily identified as PETN, points not only to the role of an al-Qaeda affiliate in Yemen but to a sophisticated bomb-maker who last year sent his brother to his death in an effort to kill a Saudi prince.

Ibrahim Hassan al-Asiri, a 28-year-old Saudi national who is on that country's most-wanted list, secreted a PETN-based bomb in a body cavity of his younger brother, Abdullah, who pretended to be turning himself in. The bomb killed his brother and wounded Mohammed bin Nayef, a top counterterrorism official and Saudi royal.

Asiri, who is based in Yemen, is also believed to have built the underwear bomb that a Nigerian man trained in Yemen attempted to detonate last Christmas Day on a commercial aircraft approaching Detroit. That device also contained PETN, or pentaerythritol trinitrate.

"He is certainly someone we are focused on," a U.S. official said of Asiri.

Both packages were shipped from Yemen, where officials said Saturday that they had arrested a woman suspected of mailing them. Her mother also was arrested.

One of the two bombs mailed from Yemen to Chicago-area synagogues traveled on two passenger flights within the Middle East, a Qatar Airways spokesman told the Associated Press Sunday.

The airline spokesman said a package containing explosives hidden in a printer cartridge arrived in Qatar Airways' hub in the capital Doha on one of the carrier's flights from Yemen, AP reported.

According to the Associated Press report, 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, the AP said. He did not give any timeframe for the two flights in question - the airline operates daily passenger flights from Yemen.

Yemeni President Ali Abdullah Saleh told reporters in the capital, Sanaa, that the United States and the United Arab Emirates had provided information that helped identify the woman who was arrested. She was arrested at her home in Sanaa.

Reuters reported that the woman, who was not named, is a medical student in her 20s.

Yemeni police arrested the woman after tracing her through a telephone number she had left with a cargo company, Reuters reported Sunday.