Impeached South Korean president Park Geun Hye spent around 14 hours being interrogated by prosecutors, a lawyer for Park says.
Park is accused of bribery, abuse of power, coercion and leaking government secrets, in a corruption scandal that has engulfed the country.
Park earlier apologised to the Korean people as she arrived at the prosecutor's office, local media reported.
"I feel sorry to the public," Park said, according to the Yonhap news agency. "I will faithfully go through the interrogation."
The country's first female president left the Blue House last week after being impeached on charges of colluding with close friend Choi Soon Sil to extort money from top South Korean companies, including Samsung, and of allowing her confidante to interfere with state affairs.
That impeachment removed the immunity that had protected Park from criminal prosecution, Yonhap said.
Park's impeachment, first rendered in December by South Korea's National Assembly, was upheld earlier this month by the country's constitutional court.
