Two women have been arrested in Yemen in connection with an apparent Al-Qaeda plot to blow up either an airplane or a Chicago synagogue – or both.

Two synagogues in Chicago were the addresses of explosives packages sent from Yemen and discovered en-route in the United Arab Emirates and Britain. One, discovered at a British airport, contained enough explosives to bring down an airplane, according to British Home Secretary Theresa May. The other, found in Dubai, the UAE's largest city, was similarly powerful.

The plot was uncovered when police were informed of the possibility of an explosive device in packages aboard a FedEx flight to Dubai. The Saudi Arabian government provided the tracking numbers of the packages, which were then tracked down and neutralized.

Yemeni sources, including a government official, said that a woman believed to be connected to the plot had been arrested in Sanaa,Yemen's capital, where the packages originated. It was later announced that the woman's mother was also arrested.

It is not clear where the bombs were meant to be detonated. "We believe that the device was designed to go off on the airplane," British Prime Minister David Cameron said, but added that there can be no certainty where this was to take place – or whether the terrorists themselves would have been able to know where the bomb was at any given time.

CNN reported that a U.S. law enforcement official said that all the packages from Yemen that authorities were looking for have been found and "no longer pose a threat." Yemen is the stronghold of Al-Qaeda in the Arabian Peninsula.

The bombs contained PETN, a highly explosive organic compound used in last year's would-be bombing of a Northwest Airlines flight near Detroit. It is estimated that each bomb contained some 400 grams of PETN – nearly 70 times the amount needed to blow a hole in the fuselage of an aircraft.

U.S. Secretary of Homeland Security Janet Napolitano said the plot appears to be an Al-Qaeda scheme. "We know that the perpetrators of this -- and it has the hallmarks of al Qaeda, the AQAP -- they are constantly trying things to test our system," she said.

The bombs, packed in toner cartridges and designed to be detonated by a cell phone, were connected via electric circuit to a mobile phone chip tucked in a printer.

U.S. President Obama thanked King Abdullah for Saudi Arabia's key role in disrupting the plot, the White House announced, while a Yemen Embassy spokesman in Washington said that Yemen is cooperating with the U.S. and England in investigating the plot. Obama's counterterrorism advisor John Brennan spoke to Yemeni President Ali Abdallah Saleh, stressing "the importance of close counterterrorism cooperation, including the need to work together on the ongoing investigation into the events over the past few days."

Meanwhile, Jewish organizations in England have been placed on high alert.