As Yemeni authorities have arrested an engineering student in connection with the plot to mail bombs to the U.S., Qater Airways say that the explosives in a package intercepted in Dubai flew on two passenger airplanes. And British Home Secretary Theresa May said the mail bomb found in the U.K. was "viable" and meant to take down the plane, though it's unclear whether the explosion was to take place over the U.K. or U.S.

According to the NY Times, the woman arrested by Yemeni authorities is Hanan Al-Samawi, a 22-year-old student at Sana University; her mother was also arrested, "Yemen’s president, Ali Abdullah Saleh, said Saturday night during a news conference that Yemeni security forces had identified her based on a tip from American officials, but he did not indicate her suspected role." Apparently she was traced by a phone number left at a shipping center.

Both bombs—which were addressed to synagogues in Chicago— had PETN, which is pentaerythritol tetranitrate. The Daily News says it's a "preferred" explosive "because it's colorless, odorless, and cannot easily be detected. It's triggered by heat or a shockwave. And just 100 grams of it is enough to destroy a car," but it does need a primary explosive for detonation.

Additionally, the bomb found in Dubai was found in a HP desktop printer; an official said, "The wiring of the device indicates that this was done by professionals. It was set up so that if you scan it, all the printer components would look right." Another official told CNN, "The thinking is it's the same person or group of people that built the underwear bomb, because of the way it's put together. But this one is about four times as powerful."

The mail bomb plot, which has the "hallmarks of Al Qaeda," has raised terror concerns in the U.S. UPS is immediately suspending cargo shipments from Yemen. At JFK Airport, passengers noticed a greater presence; a passenger said, "There are more agents walking around the terminal, looking over everything. I'm glad they're here." And at Chicago's Emanuel Congregation, one of the targeted synagogues, its rabbi said someone from Egypt visited its website over 80 times, "I think we're interesting, but not that interesting. We are planning on sharing it with the authorities."