South Korean prosecutors have grilled the country's ousted president in a long-awaited investigation of corruption allegations that ended her rule and threaten to put her in jail.
The questioning of Park Geun-hye came 11 days after the Constitutional Court unanimously ruled to dismiss her over suspicions that she colluded with a confidante to extort money from businesses and committed other wrongdoings.
Her powers had been suspended since she was impeached by parliament in December.
"I am sorry to the people. I will sincerely undergo an investigation," Park told reporters when she arrived at the prosecutors' office.
It is not clear if Park's brief statement meant she acknowledged the corruption allegations, since she has repeatedly denied any legal wrongdoing.
South Korean politicians embroiled in scandals often offer public apologies for causing trouble while still denying any involvement.
Park's questioning lasted 14 hours and ended just before midnight.
Prosecutors tried to determine whether to seek an arrest warrant, according to South Korean media. Many other suspects implicated in the scandal have already been arrested, including Park's confidante Choi Soon-sil, some senior government officials and Samsung heir Lee Jae-yong.
Prosecutors have previously accused Park of extortion, bribery and abuse of power, which could carry penalties of up to life imprisonment, but arresting her would be a delicate matter because it might aggravate a national divide and create a strong conservative backlash ahead of an election in May to choose her successor, some political experts said.
The scandal has dogged South Korea for months, with those opposing and supporting her rule staging massive rallies.
After the March 10 Constitutional Court ruling, Park supporters clashed with police, leaving three dead.
On Tuesday, hundreds of her supporters waited for hours outside the prosecutors' office, holding anti-impeachment signs and the national flag, which has become a symbol of their protest.
Park had immunity while in office and had refused to meet prosecutors or allow officials to search her presidential compound. After leaving office, she has continued to reject the allegations, saying: "I believe the truth will certainly come out."
Park is the first democratically elected leader to be forced out of office in South Korea since democracy replaced dictatorship in the late 1980s.
It was a dramatic fall for Park, the daughter of assassinated dictator Park Chung-hee, who became the country's first female president in early 2013 with the backing of conservatives who remembered her father as a hero who pulled the country up from poverty despite his suppression of civil rights.
Moon Jae-in, a liberal who lost the 2012 presidential election to Park, has a commanding lead in opinion polls for the next leader.