South Korean President Park Geun-hye bows after releasing a statement of apology to the public during a news conference at the Presidential Blue House in Seoul, South Korea, October 25, 2016. [Photo/Agencies]

Worries linger among politicians and many South Koreans about a loose investigation into Choi, whose seemingly indestructible relationship with President Park dates back to the mid-1970s.

Choi is the fifth daughter of Choi Tae-min, who reportedly approached Park serving as acting first lady following her mother's assassination in 1974.

The elder Choi, who died in 1994, is known to have been a shamanistic religious figure creating a cult called Eternal Life that combined Christianity, Roman Catholicism and Buddhism.

Rumors swirled at that time about Choi suspected of using his connections to Park to commit wrongdoings in the joint management of pro-government volunteer groups.

Choi Soon-sil said she met Park, four years older than her, for the first time at an event in 1976 when she was a college freshman, according to an interview with a local magazine in 1994. Choi has presumably cemented a close friendship with Park.

The friendship seemed to get stronger after Park's father was assassinated by the former intelligence agency chief who was one of his closest aides. Park said in her 1994 interview with the same magazine that she was grateful for Choi's father for his comfort during "the toughest times."

Choi and her father reportedly interfered with the management of the YukYoung Foundation, a non-profit fund named after Park's late mother Yuk Young-soo, since Park took office as its president in 1983.

Choi's husband Chung Yoon-hoe also served as Park's chief of staff till 2004 after Park was elected lawmaker of the Grand National Party, predecessor of the ruling Saenuri Party, in 1998.

Suspicions were raised over Chung's intervention in state affairs behind the scenes after his marriage with Choi was broken in July 2014.

Unlike Chung's case, public uproar is nonstop as local media reports speculating that Choi Soon-sil intervened in government affairs were acknowledged by President Park, who said in her public apology on Tuesday that Choi edited some of presidential speeches in her early presidency.

The president said Choi gave personal advice on speeches and public relations issues during the presidential election campaign in 2012 and during the initial presidency since February 2013. Park didn't elaborate on when Choi stopped helping her.