A South Korean court has approved an arrest warrant for a long-time friend of President Park Geun-hye.
Choi Soon-sil is suspected of using her friendship with the president to interfere in state affairs and to solicit business donations for a non-profit fund she controlled.
The allegations have prompted growing calls for President Park to resign.
Her office has announced she will make a public statement on the situation on Friday.
Ms Choi has been in custody since Monday, being questioned by prosecutors over a string of allegations.
On Thursday, a spokesman for Seoul Central District Court said it had accepted a request from prosecutors to issue an arrest warrant for Ms Choi.
Who is Choi Soon-sil?
The daughter of a shadowy religious cult leader, Choi Tae-min, who was Ms Park's mentor until his death in 1994 She became friends with Ms Park after the assassination of her father, the then President Park Chung-hee Could a friendship topple a president?
Justice Minister Kim Hyun-Woong told parliament on Thursday that Ms Park could be questioned by prosecutors if the investigation required it.
A former presidential aide, Ahn Jong-beom, has also been detained by police in the widening probe into Ms Choi's activities.
Prosecutors say they are looking into allegations that Mr Ahn and Ms Choi collaborated to force companies to donate to non-profit foundations.
Last week, Ms Park publicly apologised, admitting "certain documents" had been shared with Ms Choi and she had been allowed to edit political speeches.
"Choi advised me on expressions in my speeches and public relations during the last presidential campaign and she continued to help me for a certain period of time after I took office," Ms Park said.
"I deeply apologise to the people", she said, before bowing to the camera.
However, public anger has grown and a recent opinion poll showed her approval rating at about 9%.