Choi Soon-sil, the woman at the heart of a political controversy that has thrown the South Korean presidency into a crisis, has been put under emergency detention without a warrant, hours after she arrived at the office of local prosecutors to answer questions, according to reports.

Choi faces accusations of fraud and meddling in state affairs over her friendship with President Park Geun-hye. She was interrogated for hours on Monday after she returned to the country and turned herself in.

An official from the prosecution side told Yonhap news agency: "There is a possibility of Choi trying to destroy evidence as she is denying all the allegations. She has fled overseas in the past, and she doesn't have a permanent address in this country, making her a flight risk."

The official added: "She is also in an extremely unstable psychological state, and it's possible an unexpected event could occur if she is released." The news agency also said that she was taken to a detention facility in Seoul.

According to South Korean law, the suspect can be put under emergency detention without a warrant for 48 hours. After that, an arrest warrant needs to be issued by a court for a longer period of detention.

According to reports, she flew back from Germany to Seoul on Sunday to turn herself in for questioning. She apparently begged for forgiveness after arriving to meet prosecutors on Monday. In an interview to South Korea's Segye Ilbo newspaper, she said she saw the drafts of the president's speeches after she won the elections but rejected she had access to any other official material or that she influenced state affairs or received financial benefits.

President Park said she had given Choi the drafts of the speech early in her term and apologised for causing concern. Park and Choi have been close friends for 40 years and the nature of the friendship prompted a media frenzy in the country. On Saturday, thousands of protesters came out on the streets to demand Park's resignation.