Samsung's leader was grilled by investigators for over 22 hours in the South Korean corruption scandal

Samsung's leader Jay Y. Lee was grilled by South Korean prosecutors in a marathon 22-hour-plus session over his connection to a huge influence-peddling scandal that could topple South Korean President Park Geun-hye.

Lee did not sleep during the questioning - and neither did the two prosecutors questioning him, according to Reuters - finally leaving early on Friday morning.

Prosecutors are investigating Lee and Samsung engaged in bribery - specifically, whether the conglomerate provided 30 billion won ($25.46 million) to a business and foundations backed by President Park's friend, Choi Soon-sil, in exchange for the national pension fund's support for a 2015 merger of two Samsung affiliates.

Prosecutors are now weighing up whether to arrest the 48-year-old executive. "Lee returned home at around 7:30 a.m. this morning," a spokesperson for the special prosecutor told Bloomberg. "He has denied most of the allegations. Whether the prosecution will request an arrest warrant or not will be decided likely today or tomorrow."

The corruption scandal has engulfed the highest reaches of South Korea's elite, with President Park impeached by parliament in December. She denies wrongdoing, but has been stripped of her powers, and the decision to impeach her must now be upheld or struck down by the Constitutional Court.

Jay Y. Lee was named as a suspect on Wednesday and summoned on Thursday morning for questioning. Before the questioning, he told reporters that "I apologize to the Korean people that we couldn't show better behavior in this case," Bloomberg reported. (He did not comment after the 22-hour questioning finished.)

Prosecutors were looking into whether he gave false testimony during a parliamentary hearing in early December, where the heads of nine of South Korea's biggest chaebol (conglomerates) were subjected to an unprecedented 13-hour televised grilling by a panel investigating the presidential scandal.

Jay Y. Lee denied bribery accusations during that hearing - rejecting assertions from lawmakers that Samsung lobbied to get the fund to back the 2015 merger.

Shares in group flagship Samsung Electronics, the world's largest smartphone maker, were down about 2.5 percent on Friday.

The equestrian connection

Lee isn't the only Samsung exec that has been brought in for questioning. Park Sang-jin, a president at Samsung Electronics, was also questioned for around 13 hours until early Friday.

He's connected to a surreal aspect of the corruption scandal - an equestrian team. In 2015, Samsung Electronics sponsored an equestrian team, whose members included the daughter of Choi Soon-sil a friend of President Park who is a key figure in the scandal. Choi is in detention and undergoing a criminal trial. (She has denied wrong-doing.)

Her daughter, 20-year-old Chung Yoo-ra, was arrested by Danish police early this month after she was sought by South Korean authorities. Chung, who won a gold medal in group dressage at the 2014 Asian Games, has also denied wrongdoing.

Park Sang-jin, who had refused to appear at parliamentary hearings on the matter - citing health issues - did not comment to reporters as he left the prosecutors' office at about 3 AM while wearing a white face mask.

Two other Samsung Group executives were questioned by special prosecutors on Monday and subsequently released.

Samsung has acknowledged making payments to two foundations at the center of the scandal, as well as to a consulting firm controlled by Choi, but has repeatedly denied accusations of lobbying to push through the controversial 2015 merger of affiliates Samsung C&T Corp and Cheil Industries Inc.

Dozens of South Korean corporate groups made contributions totaling 77.4 billion won ($65.75 million) to two foundations that were set up to back President Park's initiatives, but Samsung's donations were the largest.

Late last month, the head of South Korea's National Pension Service, the world's third-largest pension fund, was arrested after he acknowledged that he had pressured the fund to approve the $8 billion merger between the two Samsung Group affiliates while he was head of the health ministry, reversing an earlier public denial.