A small amount of radioactive materials — plutonium and americium — was found in the urine of five workers exposed to radiation in an accident earlier this month at a nuclear research facility in Ibaraki Prefecture.

The result shows that the five workers have suffered internal radiation exposure following the June 6 accident at the Oarai Research & Development Center, operated by the Japan Atomic Energy Agency (JAEA).

The workers were administered medication to facilitate the discharge of radioactive materials from their bodies for five days after the accident.