“Very concrete preparations had been made for an act with a … biological bomb, which is a first for Germany,” Holger Muench, head of the Federal Criminal Police Office, told public broadcaster ARD.
German police commandos on June 12 stormed the Cologne apartment of the 29-year-old Tunisian migrant identified only as Sief Allah H. and discovered “toxic substances” that turned out to be ricin.
Produced by processing castor beans, ricin is 6,000 times more lethal than cyanide and has no known antidote.
German news weekly Der Spiegel has reported the man was thought to have been following instructions disseminated by the Islamic State group on how to build a bomb containing ricin.
Prosecutors have charged that he was “strongly suspected of intentionally manufacturing biological weapons” but it remained unclear whether he was actively plotting an attack.
Muench said “we became aware of this person a few months ago, and then evidence emerged pointing to links to the so-called Islamic State”.
The case was an example of “good cooperation between security authorities, nationally and internationally”, he said.
Bild daily has reported Germany received a tip-off from the CIA based on the suspect's online purchases.
During the raid, said Muench, “we found a large number of castor seeds from which to make it (ricin), as well as the utensils you need to make an explosive device”.
“Which concrete target he had in mind we don't know yet … and the question of possible accomplices also remains open,” said Muench.
Prosecutors say Sief Allah H. started buying the equipment and ingredients to make ricin in mid-May — including an online purchase of “a thousand castor seeds and an electric coffee grinder”.
He succeeded in manufacturing the toxin earlier this month.
The case comes less than a month after French authorities said they had foiled a terror attack possibly involving the use of ricin. Two brothers of Egyptian origin were arrested.
Germany remains on high alert after several deadly attacks claimed by the IS group, including a 2016 truck rampage through a Berlin Christmas market by Tunisian asylum seeker Anis Amri that claimed 12 lives.