The nation’s most powerful businessmen left the prosecution’s office in the wee hours of the morning Monday after hours of questioning on their alleged secret meetings with President Park Geun-hye last year.

In an unprecedented move, the prosecution summoned all eight business leaders over the weekend, while keeping much information -- including their arrival time at the office -- in strict confidence. 

Unlike other witnesses summoned over the probe, the business leaders entered the office through an underground parking space, avoiding cameras outside, according to reports.

Only close-up photos of SK Group Chairman Chey Tae-won and CJ co-Chairman Sohn Kyung-sik sitting in the backseats of their cars were released, raising questions over the prosecution offering special treatment to business leaders.

The summons were carried out fast, only two days after the investigation team said it would question the tycoons over the growing suspicions that Park had one-on-one meetings with leaders of seven South Korean conglomerates to demand money for two foundations led by her longtime friend Choi Soon-sil and her associates.

Company officials said they did not know about their leaders being questioned by the prosecution until the media reports were published.

“We learned from news reports on Sunday. We think the chairman was called in by setting the schedule confidentially,” said an official of one of the companies involved in the probe.

Among those summoned Sunday was Samsung Electronics Vice Chairman Lee Jae-yong, LG Group Chairman Koo Bon-moo and Hanjin Group Chairman Cho Yang-ho. The prosecution also questioned Hyundai Motor Group Chairman Chung Mong-koo, Hanwha Group Chairman Kim Seung-youn and SK Supex Council Chairman Kim Chang-geun on Saturday.

Samsung’s Lee left the building at around 2 a.m., after nine hours of questioning, investigators said, adding that they asked him of the purpose of the meeting he had with the president last year and whether she demanded money for the Mir and K-Sports foundations -- the two private organizations at the center of one of the biggest influence-peddling scandals in the nation’s history.

Lee was also questioned on whether he was aware about the tech giant sponsoring Widec, a sports firm owned by Choi and her daughter in Germany. According to the prosecution, Samsung Electronics, the chair company of the National Equestrian Association, transferred 3.5 billion won ($2.99 million) to Widec. Samsung offices were raided last week, followed by a questioning of a Samsung executive in charge of the company’s external affairs.

Meanwhile, SK’s Chey was not among the list of seven business leaders who met Park last year. But he was summoned because he met Park separately in February, the prosecution said in a Monday briefing.

Hanjin Chairman Cho also claimed that he did not meet Park last year, but he was questioned as part of a separate probe on whether he was pressured by former Vice Culture Minister Kim Jong to step down as chairman of the PyeongChang Winter Olympics Organizing Committee, after refusing to pick a Swiss firm associated with Choi’s firm for construction projects.

By Cho Chung-un (christory@heraldcorp.com)