A team of South Korean special prosecutors may soon raid Cheong Wa Dae, the country's presidential office, in an ongoing probe into a corruption scandal involving President Park Geun-hye, an official said Sunday.

The investigators are stepping up efforts to find evidence of Park's alleged crimes. She is suspected of colluding with her long-time friend Choi Soon-sil, now jailed, to twist the arms of business leaders to fund two non-profit foundations on culture and sports.

State prosecutors earlier alleged that Park abused her power to help Choi, who had no government post, in her campaign to raise funds and also leaked some classified state documents to her.

The allegations led the National Assembly to impeach Park in early December. The president is awaiting the final decision by the Constitutional Court on her presidential fate, with her authority suspended.

The special prosecutor's team, however, suspects that Park might have taken bribes from local conglomerates seeking business favors.

"For now, (we) can't tell you the specific timing of a raid (on Cheong Wa Dae)," Lee Kyu-chul, spokesman for the special prosecutor's office, told reporters. "(We) are still reviewing whether the raid is necessary and if so, which part should be a focus."

If there is raid of the presidential office, he added, it will be done "publicly," not secretly.

The move is apparently aimed at putting pressure on Cheong Wa Dae which has opposed a raid by prosecutors of the presidential office.

There's speculation that the investigators may seek a search warrant for Cheong Wa Dae as early as this week.

If taken, it would represent a prelude to a face-to-face interrogation of Park, the first time for prosecutors to directly question a sitting South Korean president in a criminal case.

People here hope that the special prosecutors' team will be able to reveal the truth behind all the allegations including whether Park neglected her duties in the handling of a 2014 ferry sinking that killed more than 300 passengers, mostly high school students.

Earlier in the day, meanwhile, the team summoned Jeong Ho-seong, former secretary for private presidential affairs, who was jailed on charges of leaking confidential documents to Choi. (Yonhap)