Impeached South Korean President Park Geun-hye is being questioned by prosecutors over the country’s biggest corruption scandal that brought her down.
After arriving at the office, Park Geun-hye told reporters she was “sorry”.
Park Geun-hye, 65, resisted efforts to question her when she was president, but lost her immunity when judges upheld parliament’s decision to impeach her.
The ousted leader could be charged for allegedly allowing close friend Choi Soon-sil to extort money from large companies.
Choi Soon-sil has been charged with bribery and corruption.
On March 21, Park Geun-hye’s supporters gathered outside her home in an affluent suburb of Seoul, as she was escorted by police to the prosecutors’ office in a short journey covered live on TV.
People waved the South Korean flag, a symbol of the pro-Park movement.
“I am sorry to the people. I will faithfully cooperate with questioning,” Park Geun-hye told the media when she arrived.
She is the first democratically elected leader to be ousted in South Korea.
Thousands of people celebrated in Seoul after Park Geun-hye’s removal from office on March 10. However, there were also angry protests by her supporters outside the Constitutional Court.
The court ruling was the culmination of months of political turmoil and public protest. An election now will be held by May 9.
PM Hwang Kyo-ahn, who is loyal to Park Geun-hye, is now the acting president.
At the heart of the drama lies the close friendship between Park Geun-hye and Choi Soon-sil.
Choi Soon-sil is accused of using her presidential connections to pressure companies to give millions of dollars in donations to non-profit foundations she controlled.
Park Geun-hye is alleged to have been personally involved in this, and to have given Choi Soon-sil unacceptable levels of access to official documents.
Parliament voted to impeach Park Geun-hye in December 2016.
On March 10, the Constitutional Court ruled that Park Geun-hye’s actions “seriously impaired the spirit of… democracy and the rule of law”.
Judges said she had broken the law by allowing Choi Soon-sil to meddle in state affairs, and had breached guidelines on official secrets by leaking numerous documents.
Park Geun-hye had “concealed completely Choi’s meddling in state affairs and denied it whenever suspicions over the act emerged and even criticized those who raised the suspicions,” the ruling said.
Prosecutors are now questioning Park Geun-hye in what could be a lengthy days-long process.
They had previously accused Park Geun-hye of colluding with Choi Soon-sil, which the former president has strenuously denied. She had also previously refused to take part in investigations.
After losing her presidential immunity, Park Geun-hye could be charged for abuse of power and coercion to bribery.