Updated at 5:02 p.m. on October 30.
A tip from the Saudi Arabian government led to the arrest of a woman in Yemen on suspicion of mailing the two bombs found on cargo planes in the United Arab Emirates and England, and authorities don’t believe she acted alone, sources tell National Journal. A female relative of the woman is also being questioned by Yemeni authorities, according to a Yemeni official who spoke on the condition of anonymity.
U.S. officials suspect that the terrorist group known as al-Qaida in the Arabian Peninsula was ultimately behind the attack.
"This particular plot does have the hallmarks of a AQAP plot” Homeland Security Secretary Napolitano said on the CBS Early Show. “We will trace it to its ultimate source, and we will be relentless in doing so."
Napolitano said the U.S. government believes that the plot on Friday was disrupted but she could not rule out that a larger plot is in the works. "We don't know that this was the entire universe of the plot. That's why we've taken many of the measures we've taken over the past 48 hours," she said.
A U.S. official involved in the investigation told National Journal today that more arrests are expected because it’s unlikely one person got a hold of PETN, the explosive material used in the bomb, without help. Because of the materials and devices used, a logical suspect is AQAP’s notorious bombmaker, Ibrahim Hassan al-Asiri, who is thought to be behind two previous failed plots, the alleged Christmas Day bombing attempt by Umar Farouk Abdulmutallab, a Nigerian trained in Yemen, and the attempted 2009 assassination of a Saudi minister.
For now, the U.K. government has stopped the movement of all unaccompanied airfreight originating in Yemen moving into or through the United Kingdom. Officials said no new suspicious packages had been found. The U.S. Postal Service has also suspended accepting international mail originating from Yemen, a spokeswoman for the agency said.
British Home Secretary Theresa May said the explosive component found on a UPS cargo plane at East Midlands Airport in the U.K. could have been intended to blow up the airplane itself.
"I can confirm the device was viable and could have exploded," May said. "The target of the device may have been an aircraft and, had it detonated, the aircraft could have been brought down."
May also said there is no information that another attack is imminent but added that she planned to soon talk to U.S. Homeland Security Secretary Napolitano.
White House Deputy Press Secretary Bill Burton said that Obama was briefed by counterterrorism adviser John Brennan earlier this morning before heading to Philadelphia for a campaign event. The president also placed a call to Saudi Arabia’s King Abdullah and British Prime Minister David Cameron to discuss the ongoing investigation.
Brennan told Yemeni President Ali Abdallah Saleh today that the U.S. and Yemen governments need to work together on the ongoing investigation. According to the White House, Brennan said the U.S. government “stands ready” to assist in the fight against AQAP. A U.S. official who confirmed today's arrest described it as a sign that Yemen is cooperating and taking the investigation seriously.
“Mr. Brennan also noted that Yemen’s international partners, including U.K. and Saudi Arabia, stand ready to assist the Yemeni people in developing a more stable and prosperous Yemen that will undermine al-Qa’ida’s efforts in Yemen,” the White House said.
Meanwhile, a prominent national Muslim civil rights organization praised efforts to uncover the bombing plot and condemned those responsible for coordinating it.
"We applaud the efforts of all the law enforcement and intelligence personnel who cooperated across international borders to foil a terror plot targeting Americans," said Nihad Awad, executive director of the Council on American-Islamic Relations. "We condemn both the plot and all those who would sow fear through attempts to harm the innocent."
"It is clearly against the teachings of Islam to attack places of worship. We offer our support to the American Jewish community, the apparent target of this plot," Awad added.
Aamer Madhani contributed. contributed to this article.