TAIPEI (Taiwan News) – A Navy sailor posted on a Chih Yang-class frigate was found to be holding a Chinese ID document, reports said Tuesday.

The ID was found during a search by authorities targeting Taiwanese citizens illegally holding Chinese passports or residency permits. The campaign has turned up more than 30 suspects, while about five companies helping citizens with their passport inquiries are also being investigated.

The soldier, named Yang (楊), said his Chinese mother had applied for and obtained the Chinese documents without his knowledge before he joined the military, per CNA. The Navy told the National Immigration Agency he wanted to keep his Taiwan citizenship, with the latter describing him as a special case.

Yang was originally a conscript but later registered for the military as a volunteer, serving at the Amphibious 168th Fleet based in Yilan. He emphasized that his mother had not told him about the Chinese ID and that she had obtained it when he was still a civilian. 

The Mainland Affairs Council said that serving members of the military were not allowed to live in China or apply for ID documents or any form of residence permit.

The council added that the news about Yang had been leaked before the Ministry of National Defense had completed its investigation. The authorities would act according to the outcome of the probe, the council said.