Western intelligence officials say they learned about the plot when Ahmed Sidiqi, a German citizen of Afghan descent was arrested in Afghanistan in July and taken to the U.S. airbase at Bagram for questioning. He has not been charged and intelligence sources in Germany say he is co-operating with the investigation.

In early 2009, Sidiqi and 10 others left Hamburg for the tribal areas of Pakistan — where most joined a jihadist group fighting U.S. and coalition forces across the border in Afghanistan, according to German intelligence officials…

German officials say the Hamburg group were all recruited from the Taiba mosque in Hamburg. In the 1990s. The same mosque — then called Al Quds – was attended by the lead hijacker in the 9/11 attacks, Mohammed Atta.

A friend of Atta from those days has emerged as a crucial figure in the new plot, European intelligence officials tell CNN. Naamen Meziche, 40, a French citizen of Algerian descent, worked to persuade a number of young men praying at the Taiba mosque to fight Jihad, according to the officials. His whereabouts are unknown; he is thought to be in the Afghan/Pakistan border area. Meziche’s wife told CNN that he was overseas.