TAIPEI (Taiwan News) – The recent arrival in a Taiwan port of a retired Chinese Navy captain has led to suspicions his trip might have been organized by a Chinese spy ring, the head of the country’s top intelligence agency told lawmakers Wednesday (June 12).

National Security Bureau (NSB) Director-General Tsai Ming-yen (蔡明彥) was speaking days after the former Chinese officer was arrested for entering the Tamsui River by motorboat. A clear motive for his actions has not been determined yet, though he reportedly told investigators he wanted to defect to Taiwan.

Over the past year, there have been more than a dozen cases of Chinese crossing into Taiwan illegally, Tsai said. Each time, they had been interrogated about their motives and about the route they had followed to arrive in Taiwan, the Liberty Times reported.

The phones of the Chinese arrivals played an important part in the investigation, according to Tsai. The NSB check their pictures and track down their routes based on the phones, comparing the data to ascertain whether they have been speaking the truth.

Even if their stories checked out, Tsai said he could not rule out the possibility that a network was behind their entry into Taiwan, with ships taking them close to the coast and showing them the way to the nearest port.

The intelligence chief said the NSB would improve its information about how to strengthen the border and coastlines, Radio Taiwan International (RTI) reported. Contacts with other countries to share intelligence and analyses were likely to increase in the wake of the incident in Tamsui, Tsai said.