"The mosque went back to being a very radical place where people are recruited for attacks where attacks are discussed," said former White House national security official Richard Clarke, now an ABC News consultant, "and German intelligence apparently stopped looking closely at the mosque where a lot of 9/11 was planned."
Darkazanli, who was never charged by the Germans, declined to comment about the latest plot when approached by ABC News.
In France, the Paris prosecutor's office, which is in charge of terrorism cases, has confirmed that 12 people were arrested in two separate and unrelated operations.
Two men were arrested in Marseilles and a third in Bordeaux. The three are suspected of links to Al Qaeda, and of connections to a Frenchman of Algerian origin recently arrested in Italy with explosive material. The men are suspected of offering assistance to jihadists entering France after training in the Pakistani-Afghan area.
In a separate operation, eight men and a women arrested in Marseilles are reportedly suspected of involvement in arms and explosives trafficking. Some of those arrested had already served time for "association of criminals in relation with a terrorist organization."