Police have launched a probe into Chung Sun-sin, the state investigation chief who resigned hours after it was revealed that his son had a history of school bullying.

Seoul Metropolitan Police ordered Seodaemun Police Station to investigate allegations that the National Office of Investigation chief had concealed his son's record of verbal abuse in 2017 while applying for a position to lead the office. His son was accused of verbally abusing at least two classmates at a boarding high school in Gangwon Province.

Chung faces allegations that he altered official documents and interfered with the execution of official duties by fraudulent means, both of which are considered crimes in Korea.

Chung has reportedly maintained that he was not aware that he had to include past wrongdoings surrounding him and any legal wrongdoings of his family in the application document.

This came as a civic group filed a report with the police accusing Chung, as well as National Police Agency Commissioner Yoon Hee-keun who recommended Chung as the most suitable candidate among three finalists.

Chung was appointed to become the investigation chief on Friday by President Yoon Suk Yeol but stepped down Saturday. Yoon's office admitted to "flaws" in the vetting process Sunday.

Meanwhile, the students who had allegedly been bullied by Chung's son have struggled to continue their studies in Korea, local media reported. One reportedly graduated from the boarding school but did not get into a university in Korea. The other left Korea to continue high school abroad.

Chung's son was admitted to Seoul National University, after staying a year more at the school even though he was ordered to transfer schools. His father, who was then a prosecutor, initiated litigation in 2018 in defiance of the school's order.

Of the two tracks for university admissions in Korea, only one takes into account any records of school violence, while the other only considers Suneung exam scores. Education Minister Lee Ju-ho told a radio interview Thursday that he would consider having universities require submission of any records of school violence in all admission processes.

Any incidents of school bullying or verbal abuse have come under high scrutiny in Korea, with perpetrators being shamed online. School violence has also been a major theme of TV dramas and films here, most recently in the popular series "The Glory," which was partly based on true events.

Lawmakers have also proposed a bill to extend the two-year expiration date for keeping school violence records. Under Korean rules, schools cannot retain a perpetrator's record for longer than two years unless he or she was expelled from school. A pending bill proposed in 2021 looks to extend the expiration date up to 10 years.