New York:
John O. Brennan, the president's chief counterterrorism adviser, said Sunday that American authorities believe now that the two bombs found inside cargo packages were designed to blow up the airplanes carrying them, even though they were addressed to locations "associated with synagogues" in Chicago.
"We're looking at the potential that they would have been detonated en route to those synagogues aboard the aircraft as well as at the destinations," he said in an interview on CBS's "Face the Nation." "But at this point we, I think, would agree with the British that it looks as though they were designed to be detonated in flight."
His analysis came as investigators on three continents conducted forensic studies of two bombs shipped inside computer printers from Yemen and intercepted Friday in Britain and Dubai. American officials said evidence was mounting that the top leadership of Al Qaeda in the Arabian Peninsula, including the radical American-born cleric Anwar al-Awlaki, was behind the attempted attacks.
One of the bombs traveled on two passenger planes within the Middle East before arriving in Dubai. A spokesman for Qatar Airways said that the package arrived first at the Qatar Airways hub in Doha, Qatar, on one of the airline's flights from the Yemeni capital of Sana. It was then shipped on a separate Qatar Airways passenger plane to Dubai in the United Arab Emirates, where it was discovered by authorities late Thursday or early Friday.
Mr. Brennan also said the role of the two women detained Saturday by Yemeni officials in connection with the terror plot -- a young woman and her mother -- was to deliver the packages to the United Parcel Service and FedEx offices in the capital city of Sana. An Obama administration official later said it appeared that neither woman dropped off the packages.
The younger woman was identified as Hanan Samawi, 22, an engineering student at Sana University. Ms. Samawi was freed on Sunday, according to Abdelrahman Barman, a lawyer who was in contact with her family. The government did not make a statement on the matter.
Friends who had spoken to the family said she was told by security officials that her phone number and a copy of her photo identification were found on the package. Ms. Samawi's mother was detained Saturday as well, but family friends said that was only because she insisted on accompanying her daughter.
Mr. Brennan appeared on the major Sunday news programs: CNN's "State of the Union," "Fox News Sunday," ABC's "This Week with Christiane Amanpour," NBC's "Meet the Press" and CBS's "Face the Nation." On two of the shows, he said that it remained unclear whether those behind the devices had planned for the explosives to be detonated while in the air or after arriving in Chicago.
But in his appearance on "Face the Nation," he said emphatically that it was designed to be detonated "in flight." The packages did not appear to need someone to "physically detonate them," he said on CNN, indicating that a remote or automatic detonation was possible.
Mr. Brennan said on "Meet the Press" that it was not clear whether those behind the attempted bombing had known, or could have known, whether the packages would be carried on cargo or passenger planes.
He said that authorities were not assuming that they had located all the packages involved in the attempted attack. The bombs were sophisticated and expertly constructed, American officials said Saturday, further evidence that Al Qaeda's affiliate in Yemen is steadily improving its abilities to strike on American soil.
Investigators said that the bomb discovered at the Dubai airport in the United Arab Emirates was concealed in a Hewlett-Packard desktop printer, with high explosives packed into a printer cartridge to avoid detection by scanners.
"The wiring of the device indicates that this was done by professionals," said one official involved in the investigation, who like several officials spoke on condition of anonymity because the inquiry was continuing. "It was set up so that if you scan it, all the printer components would look right."
The bomb discovered in Britain was also hidden in a printer cartridge.
The terror plot broke publicly in dramatic fashion on Friday morning, when the two packages containing explosives and addressed to synagogues or Jewish community centers in Chicago were found, setting off an international dragnet and fears about packages yet to be discovered. It also led to a tense scene in which American military jets escorted a plane to Kennedy International Airport amid concerns -- which turned out to be unfounded -- that there might be explosives on board.
American officials said their operating assumption was that the two bombs were the work of Ibrahim Hassan al-Asiri, Al Qaeda in Yemen's top bomb-maker, whose previous devices have been more rudimentary, and also unsuccessful. Mr. Asiri is believed to have built both the bomb sewn into the underwear of the young Nigerian who tried to blow up a trans-Atlantic flight last Dec. 25, and the suicide bomb that nearly killed Saudi Arabia's intelligence chief, Mohammed bin Nayef, months earlier. (In the second episode, American officials say, Mr. Asiri hid the explosives in a body cavity of his brother, the suicide bomber.)
Just as in the two previous attacks, the bomb discovered in Dubai contained the explosive PETN, according to the Dubai police and Janet Napolitano, the secretary of homeland security. This new plot, Ms. Napolitano said, had the "hallmarks of Al Qaeda."
The Department of Homeland Security issued a cable saying that the packages may have been linked to two Yemeni schools with heavy populations of foreign students. If true, that would suggest that foreign students might have been involved in the plot, as in the attempted bombing of a commercial jetliner in Detroit last Dec. 25 by a Nigerian trained in Yemen.
But the schools, listed as the Yemen-American Institute for Language-Computer Management and the American Center for Training and Development, do not appear to exist. There is a school in Sana called the Yemen American Language Institute, but it is sponsored by the U.S. State Department. Its director, Aziz al Hadi, said in a telephone interview that the school "has never used FedEx or U.P.S." and does not help foreigners to obtain visas. The school does not have a reputation for attracting religiously conservative students, unlike some other language schools in Yemen.
Many Yemenis responded to the news of the package plot, and of Ms. Samawi's arrest, with skepticism, saying they believed the whole affair could be a fabricated excuse for the United States to intervene militarily in Yemen. About 100 students protested in front of Sana University on Sunday, chanting "Freedom, freedom for Hanan!"
A friend and fellow student of Ms. Samawi, Yahya al Hammadi, said that prior to her arrest on Sunday, Ms. Samawi was having trouble with her own computer and asked some friends to help.
"How is it possible she could do all these things they say, and she can't fix her own computer?" Mr. Hammadi said.
Obama administration officials said they were discussing a range of responses to the thwarted attack. The failed attack on Dec. 25 created an opportunity for the White House to press Yemen's government to take more aggressive action against Qaeda operatives there, and some American officials believe the conditions are similar now.