Lee Jae-Yong, Samsung Electronics vice chairman and the son of the Samsung group chairman Lee Kun-Hee, has been quizzed multiple times over his role in the scandal that has rocked the nation.
The de-facto leader of Samsung narrowly avoided being formally arrested last month when prosecutors accused him of bribing Park's confidante to the tune of nearly $40 million.
A Seoul court rejected the arrest warrant on grounds of insufficient evidence.
But the prosecutors probing the scandal said Sunday that they would question Lee again after discovering additional evidence in recent weeks.
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TV footage showed the 48-year-old walking into the prosecutors' office while protestors chanted "Throw Lee Jae-Yong into jail!" and waved banners saying "Arrest Lee Jae-Yong!"
The prosecutors said earlier they would decide whether or not to seek Lee's arrest based on the outcome of Monday's questioning.
The scandal centres on Park's confidante, Choi Soon-Sil, who is accused of using her ties to the president to force local firms to "donate" nearly $70 million to two non-profit foundations which Choi allegedly used for personal gain.
Park has been named as an accomplice and is also accused of letting Choi, who has no title or security clearance, handle a wide range of state affairs including nominations of top officials.
Lee -- who has effectively taken the helm of the group since his father suffered a heart attack in 2014 -- is described as a key figure in the scandal.
Prosecutors are investigating whether Samsung's payments to Choi were aimed at securing state approval for the controversial merger of two Samsung units in 2015 -- seen as a key step towards ensuring a smooth power transfer to Lee from his father.