Samsung heir Lee Jae-Yong returned home Friday after marathon questioning by South Korean prosecutors as a suspect in a massive corruption scandal involving impeached President Park Geun-Hye.
Prosecutors said they will now decide over the weekend whether to seek a warrant and formally arrest Lee on charges of bribery and abuse of power.
Lee was named a criminal suspect Wednesday in a widening probe into an influence-peddling scandal engulfing Park and her close friend Choi Soon-Sil.
Vice chairman of Samsung Electronics and the son of Samsung Group chairman Lee Kun-Hee, he was quizzed for 22 hours over allegations of bribery.
Looking exhausted, he did not respond to questions from journalists waiting outside the special prosecutor's office as he left.
"The questioning took a long time because there were many things to check with him and because there were discrepancies" between what investigators believed had happened and Lee's statement, said prosecutor's office spokesman Lee Kyu-Chul.
If the court issues an arrest warrant Saturday or Sunday, Lee will be the first South Korean business tycoon to be arrested in the widening probe into the scandal. Three other Samsung executives may also be arrested, according to the spokesman.
More than a dozen people have already been arrested in the case, including Choi and her niece, a former culture minister, an ex-health minister, a former top presidential aide for economic affairs, and a college professor.
Business leaders grilled
In South Korea it is not unusual for suspects and witnesses to agree to a lengthy questioning session in order to avoid being repeatedly summoned by investigators.
Many suspects and witnesses in the scandal have been subjected to similar marathon questioning sessions.
They included executives from business groups such as Hyundai, SK, LG and Lotte which are being investigated for their alleged involvement in the scandal.
Choi is accused of using her ties to the president to coerce top firms into "donating" tens of millions of dollars to two non-profit foundations which Choi then used as her personal ATMs.
Samsung was the biggest contributor to the foundations.
It is also accused of separately giving millions of euros to Choi to bankroll the training of South Korean equestrian athletes in Germany, including Choi's daughter.
Prosecutors have for months questioned Lee and other senior Samsung officials to determine whether Samsung bribed Park and Choi in order to win state approval for a controversial merger which it sought in 2015.
The merger of two Samsung group units - Cheil Industries and Samsung C&T - was seen as a crucial step towards ensuring a smooth third-generation power transfer to Lee Jae-Yong.
It was criticised by many, who said it wilfully undervalued Samsung C&T's stocks. But the National Pension Service (NPS) - a major Samsung shareholder - voted in favour of the deal and it eventually went through.
The former health minister was arrested last month for allegedly pressuring NPS officials to vote in favour of the Samsung deal.
Samsung has denied allegations that it was seeking to win government favours.
South Korea's business conglomerates known as chaebol spearheaded the country's drive to prosperity from the ashes of the Korean War, but their founding families have been criticised for running their global businesses like personal fiefdoms.