An employee at Japan's nuclear safety agency lost his work phone containing sensitive information during a personal trip to China, Japanese media report.
The phone contained confidential contact details of staff involved in nuclear security work at the Nuclear Regulation Authority (NRA). The agency could not confirm if the data was leaked, reports say.
The incident comes as Japan attempts to revive its atomic energy programme, which has been stalled for more than a decade.
Japan ordered all its nuclear power plant reactors to be shut down in 2011 after a magnitude 9 earthquake and massive tsunami caused a meltdown at the Fukushima nuclear plant.
The NRA was formed after the Fukushima nuclear disaster to oversee nuclear safety, including the restarting of the country's reactors.
