TAIPEI (Kyodo) -- A former aide to Ko Wen-je, the head of Taiwan's second-largest opposition party, has been put on the wanted list for her alleged involvement in a corruption probe involving Ko, prosecutors said Friday, adding she is currently in Japan.

The Taipei District Prosecutors Office said Ko's former secretary surnamed Hsu, who left for Japan on Aug. 29, has not responded to a request for questioning over the corruption case related to a shopping center development project during Ko's tenure as Taipei mayor.

Hsu acted as Ko's private accountant, according to local media reports. The prosecutors added a request to revoke her passport has been sent to the island's Foreign Ministry.

Meanwhile, the prosecutors also sought a court approval to extend Ko's detention period, which expires next month, citing the risk that his release could complicate investigations. The former mayor who served between 2014 and 2022 was arrested on Aug. 31.

Ko unsuccessfully ran in the island's presidential election in January. His Taiwan People's Party holds the balance of power in the parliament with both the ruling Democratic Progressive Party and the main opposition Nationalist Party failing to secure a majority.