Prosecutors on Saturday summoned for questioning the sister of a key figure in the corruption scandal engulfing South Korea in the latest development relating to the investigation into the scandal. 

"Choi Soon-deuk has been under questioning from 2:00 p.m. as part of an investigation into the corruption scandal," the prosecution said in a text message sent to reporters.

Choi Soon-deuk is the elder sister of Choi Soon-sil, who is at the center of the sprawling influence-peddling scandal in which she used her decades-long ties to President Park Geun-hye to meddle in state affairs and extort money from businesses for two nonprofit organizations. 

The prosecution said it summoned her to answer a variety of questions, as she is widely believed to be involved in the scandal, although details are still sketchy. Choi Soon-deuk and the president reportedly went to the same high school.

Choi Soon-deuk is the mother of Chang Si-ho, who was arrested for pocketing profits from various deals related to the country's preparations for the 2018 PyeongChang Winter Olympic Games. 

The Choi sisters are suspected of being involved in getting illicit prescriptions for the president from a local hospital. It is illegal to issue a medical prescription without diagnosing a patient -- except for some special cases such as at the request of an immediate family member.

This month, President Park's close confidante Choi Soon-sil was arrested on charges of fraud and abuse of power. Several aides to the president were also arrested for their leading roles in the scandal.   

Park is also alleged to have directly or indirectly pressured major conglomerates into making donations to the foundations, which legal experts say could constitute an abuse of authority. 

In an about-face from her previous stance, Park refused to accept the prosecution's repeated calls for face-to-face questioning. The prosecution judged her as a key suspect in the scandal in a recent announcement. (Yonhap)