Update: Plane terror alert

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LISA MULLINS: I'm Lisa Mullins and this is The World. President Obama says investigators have uncovered a credible terrorist threat against the United States. Mr. Obama was referring to the interception of at least two packages containing explosives. The parcels were discovered in Dubai and Britain on two cargo planes headed for the United States. In a statement this afternoon at The White House, the President sought to reassure the public.

BARACK OBAMA: At this stage, the American people should know that the counterterrorism professionals are taking the threat very seriously and are taking all necessary and prudent steps to ensure our security.

MULLINS: That's President Obama speaking earlier today. The BBC's Paul Adams is covering this story from Washington. What else did the president say about all that's been transpiring today?

PAUL ADAMS: Well he did say that both of these packages were destined for what he described as places of Jewish worship in Chicago. He did not go into more detail. And he also said that both of them apparently contained explosive material. Now that's interesting because all day we've been hearing British officials talking about the device discovered at East Midlands Airport, an hour or two north of London, saying that they could not confirm that explosives were found in that package, although the authorities in Dubai have more recently said that yes indeed, explosives were found in the package intercepted there.

MULLINS: So it sounds like the packages were headed to Chicago as you said. Do we know where they originated or who the source was?

ADAMS: We know that they originated in Yemen. When the president was speaking, he said that he had spoken to the president of Yemen, Ali Abdullah Saleh, who had promised his full cooperation in an investigation. Clearly the finger of suspicion is pointing to al-Qaeda in the Arabian Peninsula. That is an al-Qaeda affiliate based in Yemen. John Brennan, the president's counterterrorism advisor said that it was the most active franchise at the moment. So that's clearly where the investigation is going to focus. And there have been some reports suggesting that both of these packages came from the same individual, an individual with known al-Qaeda contacts.

MULLINS: At this point, is there any one who is in custody?

ADAMS: No, no one is custody that we know of. Clearly this investigation is in its pretty early stages since we simply really don't yet know what kind of devices these were. Whether they were little more than letter bombs, which would be obviously a fairly limited impact, or whether they were something more sophisticated. All of this I think will come out in the coming days.

MULLINS: Okay, the BBC's Paul Adams, speaking to us from Washington, DC.