The probe into a Cheong Wa Dae document leak appears to have a hit a hurdle with police Superintendent Park Gwan-cheon, the only suspect in custody, refusing to provide further details about his actions.

With the interrogation of Park providing little results, the prosecution on Wednesday requested the courts to extend the duration of his arrest warrant by 10 days.

Park, who was assigned to the presidential office until February, is accused of removing intelligence reports he compiled from there without authorization. The prosecution believes that the documents were then copied and leaked to the media by police inspectors Choi and Han. The reports led to the so-called “Chung Yoon-hoi gate” in which Chung, a former aide of President Park Geun-hye, allegedly meddled in state affairs in collusion with presidential staff. However, the prosecution has concluded that all such allegations were groundless.

Although the prosecution suspects that Superintendent Park’s former boss Cho Eung-cheon was behind the developments, the officer is said to be refusing to provide details about the involvement of anybody else in the developments.

Cho headed Cheong Wa Dae’s department in charge of discipline within the civil service, and the presidential office had accused him of being the mastermind after an internal audit conducted earlier this month.

While Park is said to have confessed to his involvement in the leakage of Cheong Wa Dae documents to journalists, he has so far remained vague regarding Cho’s role.

Before he was taken into custody on Dec. 16, Cho told a local news outlet that he had shocking details surrounding the case but that he would not disclose the information for the time being.

Comparing himself to a zipper, Park also implied that Cho entrusted him with sensitive duties due to his ability to keep secrets.

Park is also believed to have fabricated the report that the president’s brother, Park Ji-man, had been followed by a man working for Chung.

However, Park is reported to have initially told the investigators that the so-called Park Ji-man document was compiled on the request of the president’s brother, but refuted the claims when he was questioned for the second time on Tuesday.

By Choi He-suk (cheesuk@heraldcorp.com)