The 18.1 grams of californium were seized in the northern Bolu province of the country, law enforcement officials said Saturday, according to the Daily Sabah. Five people were being investigated in regards to the incident.
The substance was seized by local anti-smuggling authorities and sent to the Turkish Atomic Energy Authority, officials said.
Californium is a rare, man-made radioactive element. First created in 1950 at the University of California at Berkeley, it's used primarily in nuclear reactors. Only the U.S. and Russia have created californium.
In March 2018, investigators seized what they thought was 1.4 kilograms of californium, but that find actually turned out to be a natural substance with no radioactivity.