By Paul Cruickshank

In late October 2010, al Qaeda in the Arabian Peninsula (AQAP) dropped off two printer bombs at UPS and FedEx offices in Yemen addressed to the United States. 

They were amongst the most sophisticated devices ever put together by al Qaeda terrorists, according to officials.

The groups chief bomb-maker Ibrahim al Asiri filled the printer cartridges of laser printers with PETN, a white powdery explosive which is difficult to detect.  He connected this explosive to a timer he hid in the circuitry of the printer.  The groups aim was to blow up the deadly cargo in planes over the eastern seaboard of the United States, but the packages were intercepted in the UK and Dubai after a tip from Saudi intelligence.  If the bombs had detonated, they had the potential to bring down the planes they were travelling on, according to authorities.

British explosive expert Sidney Alford recreates the device for CNN to demonstrate its explosive potential.  CNN has left out several critical steps from the video so as not to disclose how to assemble the bomb.  CNN's full report can be viewed online by clicking on the title above.