Turkish authorities have begun an investigation into the case of five people who were arrested in the west of the country on suspicion of smuggling radioactive material. A statement issued by the governors office in Bolu said on Sunday that five people had been arrested on suspicion of smuggling 18 grams of highly radioactive element californium used in the manufacture of nuclear warheads. Anti-smuggling and organized crime police stopped a car within the vicinity of Ataturk Park and found inside it 18.1 grams of californium hidden under the gearshift, valued at $72 million. The material was sent to the Turkish Atomic Energy Authority. Security sources said that the five suspects were being investigated to determine the source of their radioactive material and their connections inside and outside Turkey, declining to give further details. Californium is a chemical element that is not readily available in nature. It was first synthesized in the 1950s at the Lawrence Berkeley National Laboratory. In 1958, scientists first experimented with californium in concentrated form, when isotopes californium-249 to californium-252 were isolated from a sample of plutonium-239 that had been irradiated with neutrons in a nuclear reactor for five years. Later, the first californium compounds were created. Californium can be used to help start up nuclear reactors, and can also be used in the nuclear synthesis of higher mass elements. Neutrons from californium are employed as a treatment of certain cervical and brain cancers.