BioterrorismPolice carry out more raids in Cologne, Germany, after biological weapon arrest

Police in the German city of Cologne on Friday searched several empty apartments in a high-rise, following the Tuesday discovery of the highly toxic substance ricin in one of the apartments.

On Thursday, police charged a 29-year-old Tunisian man with producing a biological weapon and for “preparing a serious act of violence against the state.”

The police believe the man may have stored more ricin in other apartments in the building, and perhaps in other places in the city. local public broadcaster WDR reported that teams of specialists from the Robert Koch Institute, the German agency responsible for monitoring public health as well as diseases and infections, have been sent to various locations in the city in search for the toxin.

The Rheinische Post reported that the man, who had been under police surveillance, managed to produce enough ricin for 250 to 1,000 toxic doses, citing security sources.

Ricin is 6,000 times more powerful than cyanide, with exposure causing organ failure and death within 36 to 48 hours in 100 percent of the cases, according to the Robert Koch Institute. There is no vaccine or antidote to deal with the toxin.

Hans-Georg Maassen, the head of Germany’s domestic intelligence agency (BfV), said his agency was tipped off that a Tunisian man attempted to buy large quantities of castor seeds, the key ingredients of the highly toxic substance.

Maassen told the Rheinische Post that a look at the evidence indicates “it’s very likely a terrorist attack was possibly thwarted.”

Prosecutors said on Thursday they had not yet found evidence for planned attacks at specific times and places.