A Japanese F-15 fighter jet disappeared from radars and crashed shortly after taking off from an airbase in the central prefecture of Ishikawa on 31 January. The bodies of both pilots were found two weeks later.
Japanese news agency Kyodo reported that capsule-shaped parts containing radioactive gas Krypton-85 were in the ignition system of the engines. Both jet engines were found during the search; however, only three out of four ignition systems were found, and one of them was damaged to the point of losing the radioactive element.
In the report filed by the Japanese air force with the country's atomic energy regulator, it logged two capsules containing radioactive gas as lost, according to the news agency.
The amount of Krypton-85 in these capsules was not as significant as to pose any threat to people or the environment, the report added.