German authorities have arrested a suspect over an alleged jihadist plot to set off a chemical weapon.

Düsseldorf chief public prosecutor Holger Heming told the German media outlet SPIEGEL that authorities were originally made aware of the plot by a tip off from foreign intelligence, believed to be the FBI by other German media. According to a joint press release, police were advised that the suspect, an unnamed 32 year old Iranian citizen, had “prepared a serious act of violence that endangers the state by obtaining cyanide and castor to commit an Islamist-motivated attack.”

An operation was carried out early on Sunday, in which SEK counter terrorism operators raided the suspect’s apartment in Castrop-Rauxel. Heming told SPIEGEL that “no evidence of castor or cyanide had been found in the searched apartment” and that investigators are still determining how far the plot progressed, as well as potential targets. The suspect’s brother was also arrested in relation to the investigation. The pair had been in Germany since 2015 and previously known to authorities, but not in relation to terrorism.