TOKYO (AFP) — An employee of Japan’s nuclear regulator lost a smartphone, possibly in China, containing a confidential list of contacts, an official and local media reports said.

The case became public this week as China continues to raise pressure on Tokyo after Prime Minister Sanae Takaichi suggested in November that Japan may react militarily if Taiwan were to come under an attack.

Beijing claims the self-ruled island as part of its own territory and has not ruled out seizing it by force.

The news also came as Tokyo Electric Power (TEPCO), which operated the crippled Fukushima atomic plant, moves to restart the world’s biggest nuclear plant later this month.

The Nuclear Regulation Authority (NRA) employee’s lost work-issued smartphone is used during disasters such as major earthquakes, an agency official told Agence France-Presse (AFP) Thursday on the customary condition of anonymity.

The incident was reported in November to a Japanese body that governs proper handling of personal information, he told AFP.

The device is primarily used for telephone calls and texting, and not for accessing nuclear data at the agency, he added.

The smartphone contained the names and contact details of staff members in the authority’s nuclear security division, according to major media, including Kyodo News and the Asahi Shimbun newspaper.