South Korean President Park Geun-hye will be investigated by prosecutors probing a political corruption scandal involving her confidante and other associates. Investigators on Sunday also officially indicted Choi Soon-sil and two of Park’s former aides, who were arrested on charges of fraud, coercion and the abuse of power, CNN reported.

Lead investigator Lee Young-ryol said Park could not be charged with a crime as she was the sitting president. “But prosecutors will continue to investigate Park Geun-hye,” he said. “We have determined that President Park was an accomplice in many of the criminal acts,” Lee said, adding that investigators were basing their case on information found in notebooks, diaries and cellphones, The New York Times reported.

Prosecutors said Park colluded with Choi, a longtime friend and confidante, to extort large amounts of money in the form of donations from companies in South Korea. The money, which was transferred to non-profit foundations controlled by Choi was used for her personal gain. Park has also been accused of ordering her aides to leak official state documents to Choi, who has no official position in the South Korean government, according to The Guardian.

A spokesperson for the Blue House, Park’s executive office and official residence, said it was “regrettable” that remarks by prosecutors were giving the impression that the president had committed a crime. The spokesperson said the claims by prosecutors were “not true” and were based on “speculation and imagination”.

Park has issued several apologies for her “error” of allowing Choi access to official policy-making processes and documents. However, she has denied accusations that Choi, the daughter of a cult leader who was a close associate of Park’s father and former president Park Chung-hee, was allowed to perform “cultish rituals” within the presidential residence. Thousands of South Koreans have participated in rallies to demand her resignation.