A Tunisian detained in Germany on suspicion of planning an Islamist-motivated attack produced ricin and tested the lethal toxin on a hamster, prosecutors said on Friday.

The 29-year-old man, who was arrested in June, is suspected of building a “biological weapon” with ricin, a poison found in castor beans, the Federal Prosecutor’s Office said in a statement.

The man, named only as Sief Allah H. in line with German legal practice, bought the hamster with his wife at a pet shop in the western city of Cologne, it said, without revealing the rodent’s fate.

Investigators seized 3,150 grains of ricin - all ordered via the Internet - during a search of the suspect’s home in Cologne in June, along with 84.3 mg of prepared ricin.

Read more: Reuters