SEOUL, Jan. 22 (Xinhua) -- South Korean investigators on Wednesday were reportedly attempting to search the presidential office and residence as part of the probe into the impeached President Yoon Suk-yeol's failed martial law imposition.

The investigators said the operation was to seize a secure phone, according to Yonhap News Agency.

On Monday, in a similar raid, South Korea's police failed to search the presidential office and a so-called safe house to seize CCTV footage. Yoon was believed to have discussed his martial law imposition with officials and military commanders in the locations. ■