TOKYO (AP) — Japan’s government said Wednesday that a Japanese national has been detained in Tehran since January and demanded the Iranian authorities release them swiftly.

Deputy Chief Cabinet Secretary Masanao Ozaki, asked about foreign media reports on the case, confirmed only that the Japanese citizen was taken into custody on Jan. 20 but gave no further details, citing privacy issues.

Ozaki said the government is in contact with the detainee and their family members, while providing necessary support.

Foreign Ministry officials said the detainee is believed to be in good health, although Japanese officials have not been granted a meeting in person.

The ministry declined to comment when or on what charges the detainee was arrested.

About 200 Japanese nationals are in Iran, 150 of them in Tehran, according to the Foreign Ministry.