Lee was called in for questioning Thursday over allegations his company gave financial support to Choi in return for the government's support for a merger of two Samsung affiliates.

He returned home early Friday after being questioned for 22 hours. But the heir apparent denied most of the allegations against his own company, the official said. The investigation team will review his remarks and decide whether to seek a warrant for his arrest.

"Based on precedent, even if the bribe is given under pressure, the donor will be punished," the official said. "Lee's statement will only be a mitigating factor in the sentencing process."

Samsung signed a 22 billion-won ($18.3 million) consulting contract in August 2015 with a Germany-based firm owned by Choi and allegedly sent the company billions of won, which was used to fund her daughter's equestrian training, according to prosecutors.

The group also donated 20.4 billion won to two nonprofit foundations, allegedly linked to Choi, that were set up in October 2015 and in January 2016, respectively, becoming the biggest contributor to the Mir and K-Sports organizations created to promote Korean culture abroad and support local sports.

Prosecutors suspect Samsung supported Choi in return for the National Pension Service's approval of the controversial merger of two Samsung subsidiaries on July 17, 2015. The merger was critical in ensuring a smooth transfer of power to the heir apparent.

Lee became a board member of Samsung Electronics last October and his father, Lee Kun-hee, has been hospitalized since suffering a heart attack in 2014.

Moon Hyung-pyo, chief of the National Pension Service and former health minister, was arrested last month over his alleged role in the merger deal.

Investigators are looking into whether Park was involved in the process. Should she be found guilty of bribe-taking, it would serve as a key argument to uphold her impeachment by parliament last month.

Park met with Lee privately on July 25 of last year, but has persistently maintained there was no pressure exerted to make any donations Mir and K-Sports. The president has since argued that the direction of the prosecution's probe is biased and investigators unfairly "tied her" to whatever Choi did without her knowledge.

The impeached president has said she will prove her innocence in the Constitutional Court hearings that are currently under way to decide whether she should be be forced out of office or is reinstated. (Yonhap)