The woman at the centre of a political scandal threatening South Korea's president has been detained.
Choi Soon-sil, a long-time friend of President Park Geun-hye, is accused of influence peddling and interfering in state affairs.
Prosecutors have 48 hours since her detention on Monday to decide if they will formally arrest her.
Eight banks have also been raided in connection with the scandal, South Korean media reported.
The Yonhap news agency said the authorities were looking to confiscate documents related to Ms Choi's financial transactions.
Who is Choi Soon-sil?
- The daughter of 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
- Ms Choi, 60, has a 20-year-old daughter, Chung Yoo-ra, a female dressage rider who competed at the 2014 Asian Games
Ms Choi has been accused of embezzling money and of pressuring companies to donate to foundations she benefitted from, on the basis of her closeness to the president.
She also stands accused of involvement in high-level presidential decision making, despite lacking the security clearance required to handle classified documents.
The scandal has aroused deep anger among some South Koreans and has attracted intense media attention.
On Tuesday morning, a 45-year-old man, who said he wanted to "help Choi Soon-sil die", drove a construction vehicle into the Seoul Central District Prosecutors' office.
Ms Choi was not inside the building, but a security guard was injured in the attack and the building was damaged. The man was detained by police.
Ms Choi was placed under emergency detention late on Monday with prosecutors saying they feared she may destroy evidence.
"She has fled overseas in the past, and she doesn't have a permanent address in Korea, making her a flight risk," a prosecution official told Yonhap. "She is also in an extremely unstable psychological state."
Ms Choi told reporters on Monday that she had "committed a sin that deserves death".
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.
That did little to suppress public anger and about 8,000 people protested on Saturday, some calling for Ms Park's resignation.