The FBI are investigating an explosive device which was found on a Northwest Airlines 253 flight, that could have been used by a suicide bomber . It was seized when the United States and its partners thwarted a plot believed to be linked to al-Qaeda.

Speaking at a press conference at The Pentagon in Washington the US Defence Secretary Leon Panetta said they are still vigilant in defending the US against terrorist attacks.

One official said the latest underwear bomb to be discovered appeared to be similar to the work of fugitive Saudi militant Ibrahim Hassan al-Asiri, who U.S. sources believe is a bomb-maker working with the Yemen-based group, al Qaeda. Also responsible to be behind the so-called "underwear bomb" plot in 2009 and the 2010 attempt to blow up two cargo planes bound for the US.

The FBI told Reuters ,said it discovered the device in the past 10 days, they have possession of it and are conducting technical and forensic analysis on it.

Written and presented by Ann Salter.